M1-M8 ICT INFRA.pdf

Module 1: Single-Area OSPFv2 Concepts Enterprise Networking, Security, and Automation v7.0 (ENSA) Module Objectives Module Title: Single-Area OSPF Concepts Module Objective: Explain how single-area OSPF operates in both point-to-point and broadcast multiaccess networks. Topic Title Topic Objective OSPF Features and Describe basic OSPF features and characteristics. Characteristics OSPF Packets Describe the OSPF packet types used in single-area OSPF. OSPF Operation Explain how single-area OSPF operates. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 2 1.1 OSPF Features and Characteristics © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 3 OSPF Features and Characteristics Introduction to OSPF OSPF is a link-state routing protocol that was developed as an alternative for the distance vector Routing Information Protocol (RIP). OSPF has significant advantages over RIP in that it offers faster convergence and scales to much larger network implementations. OSPF is a link-state routing protocol that uses the concept of areas. A network administrator can divide the routing domain into distinct areas that help control routing update traffic. A link is an interface on a router, a network segment that connects two routers, or a stub network such as an Ethernet LAN that is connected to a single router. Information about the state of a link is known as a link-state. All link-state information includes the network prefix, prefix length, and cost. This module covers basic, single-area OSPF implementations and configurations. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 4 OSPF Features and Characteristics Components of OSPF All routing protocols share similar components. They all use routing protocol messages to exchange route information. The messages help build data structures, which are then processed using a routing algorithm. Routers running OSPF exchange messages to convey routing information using five types of packets: Hello packet Database description packet Link-state request packet Link-state update packet Link-state acknowledgment packet These packets are used to discover neighboring routers and also to exchange routing information to maintain accurate information about the network. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 5 OSPF Features and Characteristics Components of OSPF (Cont.) OSPF messages are used to create and maintain three OSPF databases, as follows: Database Table Description List of all neighbor routers to which a router has established bi-directional communication. Adjacency Neighbor This table is unique for each router. Database Table Can be viewed using the show ip ospf neighbor command. Lists information about all other routers in the network. Link-state Topology The database represents the network LSDB. Database Table All routers within an area have identical LSDB. (LSDB) Can be viewed using the show ip ospf database command. List of routes generated when an algorithm is run on the link-state database. Forwarding Routing Each router's routing table is unique and contains information on how and where to send Database Table packets to other routers. Can be viewed using the show ip route command. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 6 OSPF Features and Characteristics Components of OSPF (Cont.) The router builds the topology table using results of calculations based on the Dijkstra shortest-path first (SPF) algorithm. The SPF algorithm is based on the cumulative cost to reach a destination. The SPF algorithm creates an SPF tree by placing each router at the root of the tree and calculating the shortest path to each node. The SPF tree is then used to calculate the best routes. OSPF places the best routes into the forwarding database, which is used to make the routing table. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 7 OSPF Features and Characteristics Link-State Operation To maintain routing information, OSPF routers complete a generic link -state routing process to reach a state of convergence. The following are the link -state routing steps that are completed by a router: 1. Establish Neighbor Adjacencies 2. Exchange Link-State Advertisements 3. Build the Link State Database 4. Execute the SPF Algorithm 5. Choose the Best Route © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 8 OSPF Features and Characteristics Single-Area and Multiarea OSPF To make OSPF more efficient and scalable, OSPF supports hierarchical routing using areas. An OSPF area is a group of routers that share the same link-state information in their LSDBs. OSPF can be implemented in one of two ways, as follows: Single-Area OSPF - All routers are in one area. Best practice is to use area 0. Multiarea OSPF - OSPF is implemented using multiple areas, in a hierarchical fashion. All areas must connect to the backbone area (area 0). Routers interconnecting the areas are referred to as Area Border Routers (ABRs). The focus of this module is on single-area OSPFv2. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 9 OSPF Features and Characteristics Multiarea OSPF The hierarchical-topology design options with multiarea OSPF can offer the following advantages. Smaller routing tables - Tables are smaller because there are fewer routing table entries. This is because network addresses can be summarized between areas. Route summarization is not enabled by default. Reduced link-state update overhead - Designing multiarea OSPF with smaller areas minimizes processing and memory requirements. Reduced frequency of SPF calculations -– Multiarea OSPF localize the impact of a topology change within an area. For instance, it minimizes routing update impact because LSA flooding stops at the area boundary. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 10 OSPF Features and Characteristics OSPFv3 OSPFv3 is the OSPFv2 equivalent for exchanging IPv6 prefixes. OSPFv3 exchanges routing information to populate the IPv6 routing table with remote prefixes. Note: With the OSPFv3 Address Families feature, OSPFv3 includes support for both IPv4 and IPv6. OSPF Address Families is beyond the scope of this curriculum. OSPFv3 has the same functionality as OSPFv2, but uses IPv6 as the network layer transport, communicating with OSPFv3 peers and advertising IPv6 routes. OSPFv3 also uses the SPF algorithm as the computation engine to determine the best paths throughout the routing domain. OSPFv3 has separate processes from its IPv4 counterpart. The processes and operations are basically the same as in the IPv4 routing protocol, but run independently. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 11 1.2 OSPF Packets © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 12 OSPF Packets Video - OSPF Packets This video will cover the following packet types: Hello Database Description (DBD) Link-State Request (LSR) Link-State Update (LSU) Link-State Acknowledgment (LSAck) © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 13 OSPF Packets Types of OSPF Packets The table summarizes the five different types of Link State Packets (LSPs) used by OSPFv2. OSPFv3 has similar packet types. Type Packet Name Description 1 Hello Discovers neighbors and builds adjacencies between them 2 Database Description (DBD) Checks for database synchronization between routers 3 Link-State Request (LSR) Requests specific link-state records from router to router 4 Link-State Update (LSU) Sends specifically requested link-state records 5 Link-State Acknowledgment (LSAck) Acknowledges the other packet types © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 14 OSPF Packets Link-State Updates LSUs are also used to forward OSPF routing updates. An LSU packet can contain 11 different types of OSPFv2 LSAs. OSPFv3 renamed several of these LSAs and also contains two additional LSAs. LSU and LSA are often used interchangeably, but the correct hierarchy is LSU packets contain LSA messages. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 15 OSPF Packets Hello Packet The OSPF Type 1 packet is the Hello packet. Hello packets are used to do the following: Discover OSPF neighbors and establish neighbor adjacencies. Advertise parameters on which two routers must agree to become neighbors. Elect the Designated Router (DR) and Backup Designated Router (BDR) on multiaccess networks like Ethernet. Point-to- point links do not require DR or BDR. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 16 1.3 OSPF Operation © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 17 OSPF Operation Video - OSPF Operation This video will cover the 7 states of OSPF operation: Down state Init state Two-way state ExStart state Exchange state Loading state Full state © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 18 OSPF Operation OSPF Operational States State Description No Hello packets received = Down. Down State Router sends Hello packets. Transition to Init state. Hello packets are received from the neighbor. Init State They contain the Router ID of the sending router. Transition to Two-Way state. In this state, communication between the two routers is bidirectional. Two-Way State On multiaccess links, the routers elect a DR and a BDR. Transition to ExStart state. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 19 OSPF Operation OSPF Operational States (Cont.) State Description On point-to-point networks, the two routers decide which router will initiate ExStart State the DBD packet exchange and decide upon the initial DBD packet sequence number. Routers exchange DBD packets. Exchange If additional router information is required then transition to Loading; State otherwise, transition to the Full state. LSRs and LSUs are used to gain additional route information. Loading State Routes are processed using the SPF algorithm. Transition to the Full state. Full State The link-state database of the router is fully synchronized. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 20 OSPF Operation Establish Neighbor Adjacencies To determine if there is an OSPF neighbor on the link, the router sends a Hello packet that contains its router ID out all OSPF-enabled interfaces. The Hello packet is sent to the reserved All OSPF Routers IPv4 multicast address 224.0.0.5. Only OSPFv2 routers will process these packets. The OSPF router ID is used by the OSPF process to uniquely identify each router in the OSPF area. A router ID is a 32-bit number formatted like an IPv4 address and assigned to uniquely identify a router among OSPF peers. When a neighboring OSPF-enabled router receives a Hello packet with a router ID that is not within its neighbor list, the receiving router attempts to establish an adjacency with the initiating router. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 21 OSPF Operation Establish Neighbor Adjacencies (Cont.) The process routers use to establish adjacency on a multiaccess network: 1 Down to Init State When OSPFv2 is enabled on the interface, R1 transitions from Down to Init and starts sending OSPFv2 Hellos out of the interface in an attempt to discover neighbors. 2 Init State When a R2 receives a hello from the previously unknown router R1, it adds R1’s router ID to the neighbor list and responds with a Hello packet containing its own router ID. 3 Two-Way State R1 receives R2’s hello and notices that the message contains the R1 router ID in the list of R2’s neighbors. R1 adds R2’s router ID to the neighbor list and transitions to the Two- Way State. If R1 and R2 are connected with a point-to-point link, they transition to ExStart If R1 and R2 are connected over a common Ethernet network, the DR/BDR election occurs. 4 Elect the DR & BDR The DR and BDR election occurs, where the router with the highest router ID or highest priority is elected as the DR, and second highest is the BDR © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 22 OSPF Operation Synchronizing OSPF Databases After the Two-Way state, routers transition to database synchronization states. This is a three step process, as follows: Decide first router: The router with the highest router ID sends its DBD first. Exchange DBDs: As many as needed to convey the database. The other router must acknowledge each DBD with an LSAck packet. Send an LSR: Each router compares the DBD information with the local LSDB. If the DBD has more current link information, the router transitions to the loading state. After all LSRs have been exchanged and satisfied, the routers are considered synchronized and in a full state. Updates (LSUs) are sent: When a change is perceived (incremental updates) Every 30 minutes © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 23 OSPF Operation The Need for a DR Multiaccess networks can create two challenges for OSPF regarding the flooding of LSAs, as follows: Creation of multiple adjacencies - Ethernet networks could potentially interconnect many OSPF routers over a common link. Creating adjacencies with every router would lead to an excessive number of LSAs exchanged between routers on the same network. Extensive flooding of LSAs - Link-state routers flood their LSAs any time OSPF is initialized, or when there is a change in the topology. This flooding can become excessive. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 24 OSPF Operation LSA Flooding with a DR An increase in the number of routers on a multiaccess network also increases the number of LSAs exchanged between the routers. This flooding of LSAs significantly impacts the operation of OSPF. If every router in a multiaccess network had to flood and acknowledge all received LSAs to all other routers on that same multiaccess network, the network traffic would become quite chaotic. On multiaccess networks, OSPF elects a DR to be the collection and distribution point for LSAs sent and received. A BDR is also elected in case the DR fails. All other routers become DROTHERs. A DROTHER is a router that is neither the DR nor the BDR. Note: The DR is only used for the dissemination of LSAs. The router will still use the best next- hop router indicated in the routing table for the forwarding of all other packets. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 25 1.4 Module Practice and Quiz © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 26 Module Practice and Quiz What Did I Learn In This Module? Open Shortest Path First (OSPF) is a link-state routing protocol that was developed as an alternative for the distance vector Routing Information Protocol (RIP). OSPF is a link-state routing protocol that uses the concept of areas for scalability. A link is an interface on a router. A link is also a network segment that connects two routers, or a stub network such as an Ethernet LAN that is connected to a single router. All link-state information includes the network prefix, prefix length, and cost. All routing protocols use routing protocol messages to exchange route information. The messages help build data structures, which are then processed using a routing algorithm. Routers running OSPF exchange messages to convey routing information using five types of packets: the Hello packet, the database description packet, the link-state request packet, the link- state update packet, and the link-state acknowledgment packet. OSPF messages are used to create and maintain three OSPF databases: the adjacency database creates the neighbor table, the link-state database (LSDB) creates the topology table, and the forwarding database creates the routing table. The router builds the topology table using results of calculations based on the Dijkstra SPF (shortest-path first) algorithm. The SPF algorithm is based on the cumulative cost to reach a destination. In OSPF, cost is used to determine the best path to the destination. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 27 Module Practice and Quiz What Did I Learn In This Module? To maintain routing information, OSPF routers complete a generic link-state routing process to reach a state of convergence: Establish Neighbor Adjacencies, Exchange Link-State Advertisements, Build the Link State Database, Execute the SPF Algorithm, Choose the Best Route With single-area OSPF any number can be used for the area, best practice is to use area 0. Single-area OSPF is useful in smaller networks with few routers. With multiarea OSPF, one large routing domain can be divided into smaller areas, to support hierarchical routing. Routing still occurs between the areas (interarea routing), while many of the processor intensive routing operations, such as recalculating the database, are kept within an area. OSPFv3 is the OSPFv2 equivalent for exchanging IPv6 prefixes. Recall that in IPv6, the network address is referred to as the prefix and the subnet mask is called the prefix-length. OSPF uses the following link-state packets (LSPs) to establish and maintain neighbor adjacencies and exchange routing updates: 1 Hello, 2 DBD, 3 LSR, 4 LSU, and 5 LSAck. LSUs are also used to forward OSPF routing updates, such as link changes. Hello packets are used to: Discover OSPF neighbors and establish neighbor adjacencies, Advertise parameters on which two routers must agree to become neighbors, and Elect the Designated Router (DR) and Backup Designated Router (BDR) on multiaccess networks like Ethernet. Point-to- point links do not require DR or BDR. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 28 Module Practice and Quiz What Did I Learn In This Module? Some important fields in the Hello packet are type, router ID, area ID, network mask, hello interval, router priority, dead interval, DR, BDR and list of neighbors. The states that OSPF progresses through to do reach convergence are down state, init state, two- way state, ExStart state, Exchange state, loading state, and full state. When OSPF is enabled on an interface, the router must determine if there is another OSPF neighbor on the link by sending a Hello packet that contains its router ID out all OSPF-enabled interfaces. The Hello packet is sent to the reserved All OSPF Routers IPv4 multicast address 224.0.0.5. Only OSPFv2 routers will process these packets. When a neighboring OSPF-enabled router receives a Hello packet with a router ID that is not within its neighbor list, the receiving router attempts to establish an adjacency with the initiating router. After the Two-Way state, routers transition to database synchronization states, which is a three step process: Multiaccess networks can create two challenges for OSPF regarding the flooding of LSAs: the creation of multiple adjacencies and extensive flooding of LSAs. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 29 Module Practice and Quiz What Did I Learn In This Module? A dramatic increase in the number of routers also dramatically increases the number of LSAs exchanged between the routers. This flooding of LSAs significantly impact the operation of OSPF. If every router in a multiaccess network had to flood and acknowledge all received LSAs to all other routers on that same multiaccess network, the network traffic would become quite chaotic. This is why DR and BDR election is necessary. On multiaccess networks, OSPF elects a DR to be the collection and distribution point for LSAs sent and received. A BDR is also elected in case the DR fails. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 30 Module 2: Single-Area OSPFv2 Configuration Enterprise Networking, Security, and Automation v7.0 (ENSA) Module Objectives Module Title: Single-Area OSPFv2 Configuration Module Objective: Implement single-area OSPFv2 in both point-to-point and broadcast multiaccess networks. Topic Title Topic Objective OSPF Router ID Configure an OSPFv2 router ID. Point-to-Point OSPF Networks Configure single-area OSPFv2 in a point-to-point network. Configure the OSPF interface priority to influence the Multiaccess OSPF Networks DR/BDR election in a multiaccess network. Implement modifications to change the operation of single- Modify Single-Area OSPFv2 area OSPFv2. Default Route Propagation Configure OSPF to propagate a default route. Verify Single-Area OSPFv2 Verify a single-area OSPFv2 implementation. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 2 2.1 OSPF Router ID © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 3 OSPF Router ID OSPF Reference Topology The figure shows the topology used for configuring OSPFv2 in this module. The routers in the topology have a starting configuration, including interface addresses. There is currently no static routing or dynamic routing configured on any of the routers. All interfaces on R1, R2, and R3 (except the loopback 1 on R2) are within the OSPF backbone area. The ISP router is used as the gateway to the internet of the routing domain. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 4 OSPF Router ID Router Configuration Mode for OSPF OSPFv2 is enabled using the router ospf process-id global configuration mode command. The process-id value represents a number between 1 and 65,535 and is selected by the network administrator. The process-id value is locally significant. It is considered best practice to use the same process-id on all OSPF routers. R1(config)# router ospf 10 R1(config-router)# ? area OSPF area parameters auto-cost Calculate OSPF interface cost according to bandwidth default-information Control distribution of default information distance Define an administrative distance exit Exit from routing protocol configuration mode log-adjacency-changes Log changes in adjacency state neighbor Specify a neighbor router network Enable routing on an IP network no Negate a command or set its defaults passive-interface Suppress routing updates on an interface redistribute Redistribute information from another routing protocol router-id router-id for this OSPF process R1(config-router)# © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 5 OSPF Router ID Router IDs An OSPF router ID is a 32-bit value, represented as an IPv4 address. It is used to uniquely identify an OSPF router, and all OSPF packets include the router ID of the originating router. Every router requires a router ID to participate in an OSPF domain. It can be defined by an administrator or automatically assigned by the router. The router ID is used by an OSPF-enabled router to do the following: Participate in the synchronization of OSPF databases – During the Exchange State, the router with the highest router ID will send their database descriptor (DBD) packets first. Participate in the election of the designated router (DR) - In a multiaccess LAN environment, the router with the highest router ID is elected the DR. The routing device with the second highest router ID is elected the backup designated router (BDR). © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 6 OSPF Router ID Router ID Order of Precedence Cisco routers derive the router ID based on one of three criteria, in the following preferential order: 1. The router ID is explicitly configured using the OSPF router-id rid router configuration mode command. This is the recommended method to assign a router ID. 2. The router chooses the highest IPv4 address of any of configured loopback interfaces. 3. The router chooses the highest active IPv4 address of any of its physical interfaces. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 7 OSPF Router ID Configure a Loopback Interface as the Router ID Instead of relying on physical interface, the router ID can be assigned to a loopback interface. Typically, the IPv4 address for this type of loopback interface should be configured using a 32-bit subnet mask (255.255.255.255). This effectively creates a host route. A 32-bit host route would not get advertised as a route to other OSPF routers. OSPF does not need to be enabled on an interface for that interface to be chosen as the router ID. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 8 OSPF Router ID Explicitly Configure a Router ID In our reference topology the router ID for each router is assigned as follows: R1 uses router ID 1.1.1.1 R2 uses router ID 2.2.2.2 R3 uses router ID 3.3.3.3 Use the router-id rid router configuration mode command to manually assign a router ID. In the example, the router ID 1.1.1.1 is assigned to R1. Use the show ip protocols command to verify the router ID. R1(config)# router ospf 10 R1(config-router)# router-id 1.1.1.1 R1(config-router)# end *May 23 19:33:42.689: %SYS-5-CONFIG_I: Configured from console by console R1# show ip protocols | include Router ID Router ID 1.1.1.1 R1# © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 9 OSPF Router ID Modify a Router ID After a router selects a router ID, an active OSPF router does not allow the router ID to be changed until the router is reloaded or the OSPF process is reset. Clearing the OSPF process is the preferred method to reset the router ID. R1# show ip protocols | include Router ID Router ID 10.10.1.1 R1# conf t Enter configuration commands, one per line. End with CNTL/Z. R1(config)# router ospf 10 R1(config-router)# router-id 1.1.1.1 % OSPF: Reload or use "clear ip ospf process" command, for this to take effect R1(config-router)# end R1# clear ip ospf process Reset ALL OSPF processes? [no]: y *Jun 6 01:09:46.975: %OSPF-5-ADJCHG: Process 10, Nbr 3.3.3.3 on GigabitEthernet0/0/1 from FULL to DOWN, Neighbor Down: Interface down or detached *Jun 6 01:09:46.981: %OSPF-5-ADJCHG: Process 10, Nbr 3.3.3.3 on GigabitEthernet0/0/1 from LOADING to FULL, Loading Done * R1# show ip protocols | include Router ID Router ID 1.1.1.1 R1# © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 10 2.2 Point-to-Point OSPF Networks © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 11 Point-to-Point OSPF Networks The network Command Syntax You can specify the interfaces that belong to a point-to-point network by configuring the network command. You can also configure OSPF directly on the interface with the ip ospf command. The basic syntax for the network command is as follows: Router(config-router)# network network-address wildcard-mask area area-id The network-address wildcard-mask syntax is used to enable OSPF on interfaces. Any interfaces on a router that match this part of the command are enabled to send and receive OSPF packets. The area area-id syntax refers to the OSPF area. When configuring single-area OSPFv2, the network command must be configured with the same area-id value on all routers. Although any area ID can be used, it is good practice to use an area ID of 0 with single-area OSPFv2. This convention makes it easier if the network is later altered to support multiarea OSPFv2. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 12 Point-to-Point OSPF Networks The Wildcard Mask The wildcard mask is typically the inverse of the subnet mask configured on that interface. The easiest method for calculating a wildcard mask is to subtract the network subnet mask from 255.255.255.255, as shown for /24 and /26 subnet masks in the figure. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 13 Point-to-Point OSPF Networks Configure OSPF Using the network Command Within routing configuration mode, there are two ways to identify the interfaces that will participate in the OSPFv2 routing process. In the first example, the wildcard mask identifies the interface based on the network addresses. Any active interface that is configured with an IPv4 address belonging to that network will participate in the OSPFv2 routing process. Note: Some IOS versions allow the subnet mask to be entered instead of the wildcard mask. The IOS then converts the subnet mask to the wildcard mask format. R1(config)# router ospf 10 R1(config-router)# network 10.10.1.0 0.0.0.255 area 0 R1(config-router)# network 10.1.1.4 0.0.0.3 area 0 R1(config-router)# network 10.1.1.12 0.0.0.3 area 0 R1(config-router)# © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 14 Point-to-Point OSPF Networks Configure OSPF Using the network Command (Cont.) As an alternative, OSPFv2 can be enabled by specifying the exact interface IPv4 address using a quad zero wildcard mask. Entering network 10.1.1.5 0.0.0.0 area 0 on R1 tells the router to enable interface Gigabit Ethernet 0/0/0 for the routing process. The advantage of specifying the interface is that the wildcard mask calculation is not necessary. Notice that in all cases, the area argument specifies area 0. R1(config)# router ospf 10 R1(config-router)# network 10.10.1.1 0.0.0.0 area 0 R1(config-router)# network 10.1.1.5 0.0.0.0 area 0 R1(config-router)# network 10.1.1.14 0.0.0.0 area 0 R1(config-router)# © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 15 Point-to-Point OSPF Networks Configure OSPF Using the ip ospf Command To configure OSPF directly on the interface, use the ip ospf interface configuration mode command. The syntax is as follows: Router(config-if)# ip ospf process-id area area-id Remove the network commands using the no form of the command. Then go to each interface and configure the ip ospf command R1(config)# router ospf 10 R1(config-router)# no network 10.10.1.1 0.0.0.0 area 0 R1(config-router)# no network 10.1.1.5 0.0.0.0 area 0 R1(config-router)# no network 10.1.1.14 0.0.0.0 area 0 R1(config-router)# interface GigabitEthernet 0/0/0 R1(config-if)# ip ospf 10 area 0 R1(config-if)# interface GigabitEthernet 0/0/1 R1(config-if)# ip ospf 10 area 0 R1(config-if)# interface Loopback 0 R1(config-if)# ip ospf 10 area 0 R1(config-if)# © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 16 Point-to-Point OSPF Networks Passive Interface By default, OSPF messages are forwarded out all OSPF-enabled interfaces. However, these messages only need to be sent out interfaces that are connecting to other OSPF- enabled routers. Sending out unneeded messages on a LAN affects the network in three ways: Inefficient Use of Bandwidth - Available bandwidth is consumed transporting unnecessary messages. Inefficient Use of Resources - All devices on the LAN must process and eventually discard the message. Increased Security Risk - Without additional OSPF security configurations, OSPF messages can be intercepted with packet sniffing software. Routing updates can be modified and sent back to the router, corrupting the routing table with false metrics that misdirect traffic. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 17 Point-to-Point OSPF Networks Configure Passive Interfaces Use the passive- interface router configuration mode command to prevent the transmission of routing messages through a router interface, but still allow that network to be advertised to other routers. The show ip protocols command is then used to verify that the interface is listed as passive. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 18 Point-to-Point OSPF Networks OSPF Point-to-Point Networks By default, Cisco routers elect a DR and BDR on Ethernet interfaces, even if there is only one other device on the link. You can verify this with the show ip ospf interface command. The DR/ BDR election process is unnecessary as there can only be two routers on the point-to-point network between R1 and R2. Notice in the output that the router has designated the network type as BROADCAST. R1# show ip ospf interface GigabitEthernet 0/0/0 GigabitEthernet0/0/0 is up, line protocol is up Internet Address 10.1.1.5/30, Area 0, Attached via Interface Enable Process ID 10, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 1 Topology-MTID Cost Disabled Shutdown Topology Name 0 1 no no Base Enabled by interface config, including secondary ip addresses Transmit Delay is 1 sec, State BDR, Priority 1 Designated Router (ID) 2.2.2.2, Interface address 10.1.1.6 Backup Designated router (ID) 1.1.1.1, Interface address 10.1.1.5 Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5 oob-resync timeout 40 © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 19 Point-to-Point OSPF Networks OSPF Point-to-Point Networks (Cont.) To change this to a point-to-point network, use the interface configuration command ip ospf network point-to-point on all interfaces where you want to disable the DR/BDR election process. R1(config)# interface GigabitEthernet 0/0/0 R1(config-if)# ip ospf network point-to-point *Jun 6 00:44:05.208: %OSPF-5-ADJCHG: Process 10, Nbr 2.2.2.2 on GigabitEthernet0/0/0 from FULL to DOWN, Neighbor Down: Interface down or detached *Jun 6 00:44:05.211: %OSPF-5-ADJCHG: Process 10, Nbr 2.2.2.2 on GigabitEthernet0/0/0 from LOADING to FULL, Loading Done R1(config-if)# end R1# show ip ospf interface GigabitEthernet 0/0/0 GigabitEthernet0/0/0 is up, line protocol is up Internet Address 10.1.1.5/30, Area 0, Attached via Interface Enable Process ID 10, Router ID 1.1.1.1, Network Type POINT_TO_POINT, Cost: 1 Topology-MTID Cost Disabled Shutdown Topology Name © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 20 Point-to-Point OSPF Networks Loopbacks and Point-to-Point Networks Use loopbacks to provide additional interfaces for a variety of purposes. By default, loopback interfaces are advertised as /32 host routes. To simulate a real LAN, the loopback interface can be configured as a point-to-point network to advertise the full network. What R2 sees when R1 advertises the loopback interface as-is: R2# show ip route | include 10.10.1 O 10.10.1.1/32 [110/2] via 10.1.1.5, 00:03:05, GigabitEthernet0/0/0 Configuration change at R1: R1(config-if)# interface Loopback 0 R1(config-if)# ip ospf network point-to-point Result at R2: R2# show ip route | include 10.10.1 O 10.10.1.0/24 [110/2] via 10.1.1.5, 00:03:05, GigabitEthernet0/0/0 © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 21 Point-to-Point OSPF Networks Packet Tracer - Point-to-Point Single-Area OSPFv2 Configuration In this Packet Tracer activity, you will do the following: Explicitly configure router IDs. Configure the network command on R1 using wildcard mask based on the subnet mask. Configure the network command on R2 using a quad-zero wildcard mask. Configure the ip ospf interface command on R3. Configure passive interfaces. Verify OSPF operation using the show ip protocols and show ip route commands. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 22 2.3 Multiaccess OSPF Networks © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 23 Multiaccess OSPF Networks OPSF Network Types Another type of network that uses OSPF is the multiaccess OSPF network. Multiaccess OSPF networks are unique in that one router controls the distribution of LSAs. The router that is elected for this role should be determined by the network administrator through proper configuration. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 24 Multiaccess OSPF Networks OPSF Designated Router In multiaccess networks, OSPF elects a DR and BDR. The DR is responsible for collecting and distributing LSAs sent and received. The DR uses the multicast IPv4 address 224.0.0.5 which is meant for all OSPF routers. A BDR is also elected in case the DR fails. The BDR listens passively and maintains a relationship with all the routers. If the DR stops producing Hello packets, the BDR promotes itself and assumes the role of DR. All other routers become a DROTHER (a router that is neither the DR nor the BDR). DROTHERs use the multiaccess address 224.0.0.6 (all designated routers) to send OSPF packets to the DR and BDR. Only the DR and BDR listen for 224.0.0.6. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 25 Multiaccess OSPF Networks OPSF Multiaccess Reference Topology In the multiaccess topology shown in the figure, there are three routers interconnected over a common Ethernet multiaccess network, 192.168.1.0/24. Because the routers are connected over a common multiaccess network, OSPF has automatically elected a DR and BDR. R3 has been elected as the DR because its router ID is 3.3.3.3, which is the highest in this network. R2 is the BDR because it has the second highest router ID in the network. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 26 Multiaccess OSPF Networks Verify OSPF Router Roles To verify the roles of the OSPFv2 router, use the show ip ospf interface command. The output generated by R1 confirms that the following: R1 is not the DR or BDR, but is a DROTHER with a default priority of 1. (Line 7) The DR is R3 with router ID 3.3.3.3 at IPv4 address 192.168.1.3, while the BDR is R2 with router ID 2.2.2.2 at IPv4 address 192.168.1.2. (Lines 8 and 9) R1 has two adjacencies: one with the BDR and one with the DR. (Lines 20-22) R1# show ip ospf interface GigabitEthernet 0/0/0 GigabitEthernet0/0/0 is up, line protocol is up Internet Address 192.168.1.1/24, Area 0, Attached via Interface Enable Process ID 10, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 1 (output omitted) Transmit Delay is 1 sec, State DROTHER, Priority 1 Designated Router (ID) 3.3.3.3, Interface address 192.168.1.3 Backup Designated router (ID) 2.2.2.2, Interface address 192.168.1.2 (output omitted) Neighbor Count is 2, Adjacent neighbor count is 2 Adjacent with neighbor 2.2.2.2 (Backup Designated Router) Adjacent with neighbor 3.3.3.3 (Designated Router) Suppress hello for 0 neighbor(s) R1# © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 27 Multiaccess OSPF Networks Verify OSPF Router Roles (Cont.) The output generated by R2 confirms that: R2 is the BDR with a default priority of 1. (Line 7) The DR is R3 with router ID 3.3.3.3 at IPv4 address 192.168.1.3, while the BDR is R2 with router ID 2.2.2.2 at IPv4 address 192.168.1.2. (Lines 8 and 9) R2 has two adjacencies; one with a neighbor with router ID 1.1.1.1 (R1) and the other with the DR. (Lines 20-22) R2# show ip ospf interface GigabitEthernet 0/0/0 GigabitEthernet0/0/0 is up, line protocol is up Internet Address 192.168.1.2/24, Area 0, Attached via Interface Enable Process ID 10, Router ID 2.2.2.2, Network Type BROADCAST, Cost: 1 (output omitted) Transmit Delay is 1 sec, State BDR, Priority 1 Designated Router (ID) 3.3.3.3, Interface address 192.168.1.3 Backup Designated Router (ID) 2.2.2.2, Interface address 192.168.1.2 (output omitted) Neighbor Count is 2, Adjacent neighbor count is 2 Adjacent with neighbor 1.1.1.1 Adjacent with neighbor 3.3.3.3 (Designated Router) Suppress hello for 0 neighbor(s) R2# © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 28 Multiaccess OSPF Networks Verify OSPF Router Roles (Cont.) The output generated by R3 confirms that: R3 is the DR with a default priority of 1. (Line 7) The DR is R3 with router ID 3.3.3.3 at IPv4 address 192.168.1.3, while the BDR is R2 with router ID 2.2.2.2 at IPv4 address 192.168.1.2. (Lines 8 and 9) R3 has two adjacencies: one with a neighbor with router ID 1.1.1.1 (R1) and the other with the BDR. (Lines 20-22) R1# show ip ospf interface GigabitEthernet 0/0/0 GigabitEthernet0/0/0 is up, line protocol is up Internet Address 192.168.1.1/24, Area 0, Attached via Interface Enable Process ID 10, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 1 (output omitted) Transmit Delay is 1 sec, State DROTHER, Priority 1 Designated Router (ID) 3.3.3.3, Interface address 192.168.1.3 Backup Designated router (ID) 2.2.2.2, Interface address 192.168.1.2 (output omitted) Neighbor Count is 2, Adjacent neighbor count is 2 Adjacent with neighbor 2.2.2.2 (Backup Designated Router) Adjacent with neighbor 3.3.3.3 (Designated Router) Suppress hello for 0 neighbor(s) R1# © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 29 Multiaccess OSPF Networks Verify DR/BDR Adjacencies To verify the OSPFv2 adjacencies, use the show ip ospf neighbor command. The state of neighbors in multiaccess networks can be as follows: FULL/DROTHER - This is a DR or BDR router that is fully adjacent with a non-DR or BDR router. These two neighbors can exchange Hello packets, updates, queries, replies, and acknowledgments. FULL/DR - The router is fully adjacent with the indicated DR neighbor. These two neighbors can exchange Hello packets, updates, queries, replies, and acknowledgments. FULL/BDR - The router is fully adjacent with the indicated BDR neighbor. These two neighbors can exchange Hello packets, updates, queries, replies, and acknowledgments. 2-WAY/DROTHER - The non-DR or BDR router has a neighbor relationship with another non-DR or BDR router. These two neighbors exchange Hello packets. The normal state for an OSPF router is usually FULL. If a router is stuck in another state, it is an indication that there are problems in forming adjacencies. The only exception to this is the 2-WAY state, which is normal in a multiaccess broadcast network. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 30 Multiaccess OSPF Networks Verify DR/BDR Adjacencies (Cont.) The output generated by R2 confirms that R2 has adjacencies with the following routers: R1 with router ID 1.1.1.1 is in a Full state and R1 is neither the DR nor BDR. R3 with router ID 3.3.3.3 is in a Full state and the role of R3 is DR. R2# show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 1.1.1.1 1 FULL/DROTHER 00:00:31 192.168.1.1 GigabitEthernet0/0/0 3.3.3.3 1 FULL/DR 00:00:34 192.168.1.3 GigabitEthernet0/0/0 R2# © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 31 Multiaccess OSPF Networks Default DR/BDR Election Process The OSPF DR and BDR election is based on the following criteria, in sequential order: 1. The routers in the network elect the router with the highest interface priority as the DR. The router with the second highest interface priority is becomes the BDR. The priority can be configured to be any number between 0 – 255. If the interface priority value is set to 0, that interface cannot be elected as DR nor BDR. The default priority of multiaccess broadcast interfaces is 1. 2. If the interface priorities are equal, then the router with the highest router ID is elected the DR. The router with the second highest router ID is the BDR. The election process takes place when the first router with an OSPF-enabled interface is active on the network. If all of the routers on the network have not finished booting, it is possible that a router with a lower router ID becomes the DR. The addition of a new router does not initiate a new election process. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 32 Multiaccess OSPF Networks DR Failure and Recovery After the DR is elected, it remains the DR until one of the following events occurs: The DR fails. The OSPF process on the DR fails or is stopped. The multiaccess interface on the DR fails or is shutdown. If the DR fails, the BDR is automatically promoted to DR. This is the case even if another DROTHER with a higher priority or router ID is added to the network after the initial DR/BDR election. However, after a BDR is promoted to DR, a new BDR election occurs and the DROTHER with the highest priority or router ID is elected as the new BDR. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 33 Multiaccess OSPF Networks The ip ospf priority Command If the interface priorities are equal on all routers, the router with the highest router ID is elected the DR. Instead of relying on the router ID, it is better to control the election by setting interface priorities. This also allows a router to be the DR in one network and a DROTHER in another. To set the priority of an interface, use the command ip ospf priority value, where value is 0 to 255. A value of 0 does not become a DR or a BDR. A value of 1 to 255 on the interface makes it more likely that the router becomes the DR or the BDR. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 34 Multiaccess OSPF Networks Configure OSPF Priority The example shows the commands being used to change the R1 G0/0/0 interface priority from 1 to 255 and then reset the OSPF process. R1(config)# interface GigabitEthernet 0/0/0 R1(config-if)# ip ospf priority 255 R1(config-if)# end R1# clear ip ospf process Reset ALL OSPF processes? [no]: y R1# *Jun 5 03:47:41.563: %OSPF-5-ADJCHG: Process 10, Nbr 2.2.2.2 on GigabitEthernet0/0/0 from FULL to DOWN, Neighbor Down: Interface down or detached © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 35 Multiaccess OSPF Networks Packet Tracer - Determine the DR and BDR In this activity, you will complete the following: Examine DR and BDR roles and watch the roles change when there is a change in the network. Modify the priority to control the roles and force a new election. Verify routers are filling the desired roles © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 36 2.4 Modify Single-Area OSPFv2 © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 37 Modify Single-Area OSPFv2 Cisco OSPF Cost Metric Routing protocols use a metric to determine the best path of a packet across a network. OSPF uses cost as a metric. A lower cost indicates a better path. The Cisco cost of an interface is inversely proportional to the bandwidth of the interface. Therefore, a higher bandwidth indicates a lower cost. The formula used to calculate the OSPF cost is: Cost = reference bandwidth / interface bandwidth The default reference bandwidth is 10 8 (100,000,000); therefore, the formula is: Cost = 100,000,000 bps / interface bandwidth in bps Because the OSPF cost value must be an integer, FastEthernet, Gigabit Ethernet, and 10 GigE interfaces share the same cost. To correct this situation, you can: Adjust the reference bandwidth with the auto-cost reference-bandwidth command on each OSPF router. Manually set the OSPF cost value with the ip ospf cost command on necessary interfaces. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 38 Modify Single-Area OSPFv2 Cisco OSPF Cost Metric (Cont.) Refer to the table for a breakdown of the cost calculation © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 39 Modify Single-Area OSPFv2 Adjust the Reference Bandwidth The cost value must be an integer. If something less than an integer is calculated, OSPF rounds up to the nearest integer. Therefore, the OSPF cost assigned to a Gigabit Ethernet interface with the default reference bandwidth of 100,000,000 bps would equal 1, because the nearest integer for 0.1 is 0 instead of 1. Cost = 100,000,000 bps / 1,000,000,000 = 1 For this reason, all interfaces faster than Fast Ethernet will have the same cost value of 1 as a Fast Ethernet interface. To assist OSPF in making the correct path determination, the reference bandwidth must be changed to a higher value to accommodate networks with links faster than 100 Mbps. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 40 Modify Single-Area OSPFv2 Adjust the Reference Bandwidth (Cont.) Changing the reference bandwidth does not actually affect the bandwidth capacity on the link; rather, it simply affects the calculation used to determine the metric. To adjust the reference bandwidth, use the auto-cost reference-bandwidth Mbps router configuration command. This command must be configured on every router in the OSPF domain. Notice in the command that the value is expressed in Mbps; therefore, to adjust the costs for Gigabit Ethernet, use the command auto-cost reference-bandwidth 1000. For 10 Gigabit Ethernet, use the command auto-cost reference-bandwidth 10000. To return to the default reference bandwidth, use the auto-cost reference-bandwidth 100 command. Another option is to change the cost on one specific interface using the ip ospf cost cost command. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 41 Modify Single-Area OSPFv2 Adjust the Reference Bandwidth (Cont.) Whichever method is used, it is important to apply the configuration to all routers in the OSPF routing domain. The table shows the OSPF cost if the reference bandwidth is adjusted to accommodate 10 Gigabit Ethernet links. The reference bandwidth should be adjusted anytime there are links faster than FastEthernet (100 Mbps). Use the show ip ospf interface command to verify the current OSPFv2 cost assigned to the interface. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 42 Modify Single-Area OSPFv2 OSPF Accumulates Cost The cost of an OSPF route is the accumulated value from one router to the destination network. Assuming the auto-cost reference-bandwidth 10000 command has been configured on all three routers, the cost of the links between each router is now 10. The loopback interfaces have a default cost of 1. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 43 Modify Single-Area OSPFv2 OSPF Accumulates Cost (Cont.) You can calculate the cost for each router to reach each network. For example, the total cost for R1 to reach the 10.10.2.0/24 network is 11. This is because the link to R2 cost = 10 and the loopback default cost = 1. 10 + 1 = 11. You can verify this with the show ip route command. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 44 Modify Single-Area OSPFv2 OSPF Accumulates Cost (Cont.) Verifying the accumulated cost for the path to the 10.10.2.0/24 network: R1# show ip route | include 10.10.2.0 O 10.10.2.0/24 [110/11] via 10.1.1.6, 01:05:02, GigabitEthernet0/0/0 R1# show ip route 10.10.2.0 Routing entry for 10.10.2.0/24 Known via "ospf 10", distance 110, metric 11, type intra area Last update from 10.1.1.6 on GigabitEthernet0/0/0, 01:05:13 ago Routing Descriptor Blocks: * 10.1.1.6, from 2.2.2.2, 01:05:13 ago, via GigabitEthernet0/0/0 Route metric is 11, traffic share count is 1 R1# © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 45 Modify Single-Area OSPFv2 Manually Set OSPF Cost Value Reasons to manually set the cost value include: The Administrator may want to influence path selection within OSPF, causing different paths to be selected than what normally would given default costs and cost accumulation. Connections to equipment from other vendors who use a different formula to calculate OSPF cost. To change the cost value reported by the local OSPF router to other OSPF routers, use the interface configuration command ip ospf cost value. R1(config)# interface g0/0/1 R1(config-if)# ip ospf cost 30 R1(config-if)# interface lo0 R1(config-if)# ip ospf cost 10 R1(config-if)# end R1# © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 46 Modify Single-Area OSPFv2 Test Failover to Backup Route What happens if the link between R1 and R2 goes down? You can simulate that by shutting down the Gigabit Ethernet 0/0/0 interface and verifying the routing table is updated to use R3 as the next-hop router. Notice that R1 can now reach the 10.1.1.4/30 network through R3 with a cost value of 50. R1# show ip route ospf | begin 10 10.0.0.0/8 is variably subnetted, 8 subnets, 3 masks O 10.1.1.4/30 [110/50] via 10.1.1.13, 00:00:14, GigabitEthernet0/0/1 O 10.1.1.8/30 [110/40] via 10.1.1.13, 00:00:14, GigabitEthernet0/0/1 O 10.10.2.0/24 [110/50] via 10.1.1.13, 00:00:14, GigabitEthernet0/0/1 O 10.10.3.0/24 [110/40] via 10.1.1.13, 00:00:14, GigabitEthernet0/0/1 R1# © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 47 Modify Single-Area OSPFv2 Hello Packet Intervals OSPFv2 Hello packets are transmitted to multicast address 224.0.0.5 (all OSPF routers) every 10 seconds. This is the default timer value on multiaccess and point-to- point networks. Note: Hello packets are not sent on interfaces set to passive by the passive-interface command. The Dead interval is the period that the router waits to receive a Hello packet before declaring the neighbor down. If the Dead interval expires before the routers receive a Hello packet, OSPF removes that neighbor from its link-state database (LSDB). The router floods the LSDB with information about the down neighbor out all OSPF- enabled interfaces. Cisco uses a default of 4 times the Hello interval. This is 40 seconds on multiaccess and point-to-point networks. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 48 Modify Single-Area OSPFv2 Verify Hello and Dead Intervals The OSPF Hello and Dead intervals are configurable on a per-interface basis. The OSPF intervals must match or a neighbor adjacency does not occur. To verify the currently configured OSPFv2 interface intervals, use the show ip ospf interface command. The Gigabit Ethernet 0/0/0 Hello and Dead intervals are set to the default 10 seconds and 40 seconds respectively. R1# show ip ospf interface g0/0/0 GigabitEthernet0/0/0 is up, line protocol is up Internet Address 10.1.1.5/30, Area 0, Attached via Interface Enable Process ID 10, Router ID 1.1.1.1, Network Type POINT_TO_POINT, Cost: 10 Topology-MTID Cost Disabled Shutdown Topology Name 0 10 no no Base Enabled by interface config, including secondary ip addresses Transmit Delay is 1 sec, State POINT_TO_POINT Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5 oob-resync timeout 40 (output omitted) © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 49 Modify Single-Area OSPFv2 Verify Hello and Dead Intervals (Cont.) Use the show ip ospf neighbor command to see the Dead Time counting down from 40 seconds. By default, this value is refreshed every 10 seconds when R1 receives a Hello from the neighbor. R1# show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 3.3.3.3 0 FULL/ - 00:00:35 10.1.1.13 GigabitEthernet0/0/1 2.2.2.2 0 FULL/ - 00:00:31 10.1.1.6 GigabitEthernet0/0/0 R1# © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 50 Modify Single-Area OSPFv2 Modify OSPFv2 Intervals It may be desirable to change the OSPF timers so that routers detect network failures in less time. Doing this increases traffic, but sometimes the need for quick convergence is more important than the extra traffic it creates. Note: The default Hello and Dead intervals are based on best practices and should only be altered in rare situations. OSPFv2 Hello and Dead intervals can be modified manually using the following interface configuration mode commands: Router(config-if)# ip ospf hello-interval seconds Router(config-if)# ip ospf dead-interval seconds Use the no ip ospf hello-interval and no ip ospf dead-interval commands to reset the intervals to their default. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 51 Modify Single-Area OSPFv2 Modify OSPFv2 Intervals (Cont.) In the example, the Hello interval for the link between R1 and R2 is changed to 5 seconds. The Cisco IOS automatically modifies the Dead interval to four times the Hello interval. However, you can document the new Dead interval in the configuration by manually setting it to 20 seconds, as shown. When the Dead Timer on R1 expires, R1 and R2 lose adjacency. R1 and R2 must be configured with the same Hello interval. Use the show ip ospf neighbor command on R1 to verify the neighbor adjacencies. R1(config)# interface g0/0/0 R1(config-if)# ip ospf hello-interval 5 R1(config-if)# ip ospf dead-interval 20 R1(config-if)# *Jun 7 04:56:07.571: %OSPF-5-ADJCHG: Process 10, Nbr 2.2.2.2 on GigabitEthernet0/0/0 from FULL to DOWN, Neighbor Down: Dead timer expired R1(config-if)# end R1# show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 3.3.3.3 0 FULL/ - 00:00:37 10.1.1.13 GigabitEthernet0/0/1 R1# © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 52 Modify Single-Area OSPFv2 Packet Tracer - Modify Single-Area OSPFv2 In this Packet Tracer activity, you will complete the following: Adjust the reference bandwidth to account for gigabit and faster speeds Modify the OSPF cost value Modify the OSPF Hello timers Verify the modifications are accurately reflected in the routers. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 53 2.5 Default Route Propagation © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 54 Default Route Propagation Propagate a Default Static Route in OSPFv2 To propagate a default route, the edge router must be configured with the following: A default static route using the ip route 0.0.0.0 0.0.0.0 [next-hop-address | exit-intf] command. The default-information originate router configuration command. This instructs R2 to be the source of the default route information and propagate the default static route in OSPF updates. In the example, R2 is configured with a loopback to simulate a connection to the internet. A default route is configured and propagated to all other OSPF routers in the routing domain. Note: When configuring static routes, best practice is to use the next-hop IP address. However, when simulating a connection to the internet, there is no next-hop IP address. Therefore, we use the exit-intf argument. R2(config)# interface lo1 R2(config-if)# ip address 64.100.0.1 255.255.255.252 R2(config-if)# exit R2(config)# ip route 0.0.0.0 0.0.0.0 loopback 1 %Default route without gateway, if not a point-to-point interface, may impact performance R2(config)# router ospf 10 R2(config-router)# default-information originate R2(config-router)# end R2# © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 55 Default Route Propagation Verify the Propagated Default Route You can verify the default route settings on R2 using the show ip route command. You can also verify that R1 and R3 received a default route. Notice that the route source on R1 is O*E2, signifying that it was learned using OSPFv2. The asterisk identifies this as a good candidate for the default route. The E2 designation identifies that it is an external route. The meaning of E1 and E2 is beyond the scope of this module. R2# show ip route | begin Gateway Gateway of last resort is 0.0.0.0 to network 0.0.0.0 S* 0.0.0.0/0 is directly connected, Loopback1 10.0.0.0/8 is variably subnetted, 9 subnets, 3 masks (output omitted) R1# show ip route | begin Gateway Gateway of last resort is 10.1.1.6 to network 0.0.0.0 O*E2 0.0.0.0/0 [110/1] via 10.1.1.6, 00:11:08, GigabitEthernet0/0/0 10.0.0.0/8 is variably subnetted, 9 subnets, 3 masks (output omitted) © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 56 Default Route Propagation Packet Tracer - Propagate a Default Route in OSPFv2 In this Packet Tracer, you will complete the following: Propagate a Default Route Part 2: Verify Connectivity © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 57 2.6 Verify Single-Area OSPFv2 © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 58 Verify Single-Area OSPFv2 Verify OSPF Neighbors After configuring single-area OSPFv2, you will need to verify your configurations. The following two commands are particularly useful for verifying routing: show ip interface brief - This verifies that the desired interfaces are active with correct IP addressing. show ip route- This verifies that the routing table contains all the expected routes. Additional commands for determining that OSPF is operating as expected include the following: show ip ospf neighbor show ip protocols show ip ospf show ip ospf interface © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 59 Verify Single-Area OSPFv2 Verify OSPF Neighbors (Cont.) Use the show ip ospf neighbor command to verify that the router has formed an adjacency with its neighboring routers. If the router ID of the neighboring router is not displayed, or if it does not show as being in a state of FULL, the two routers have not formed an OSPFv2 adjacency. Note: A non-DR or BDR router that has a neighbor relationship with another non-DR or BDR router will display a two-way adjacency instead of full. The following command output displays the neighbor table of R1. R1# show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 3.3.3.3 0 FULL/ - 00:00:35 10.1.1.13 GigabitEthernet0/0/1 2.2.2.2 0 FULL/ - 00:00:31 10.1.1.6 GigabitEthernet0/0/0 R1# © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 60 Verify Single-Area OSPFv2 Verify OSPF Neighbors (Cont.) Two routers may not form an OSPFv2 adjacency if the following occurs: The subnet masks do not match, causing the routers to be on separate networks. The OSPFv2 Hello or Dead Timers do not match. The OSPFv2 Network Types do not match. There is a missing or incorrect OSPFv2 network command. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 61 Verify Single-Area OSPFv2 Verify OSPF Protocol Settings The show ip protocols R1# show ip protocols command is a quick way to *** IP Routing is NSF aware *** (output omitted) verify vital OSPF Routing Protocol is "ospf 10" configuration information, as Outgoing update filter list for all interfaces is not set shown in the command Incoming update filter list for all interfaces is not set Router ID 1.1.1.1 output. This includes the Number of areas in this router is 1. 1 normal 0 stub 0 nssa OSPFv2 process ID, the Maximum path: 4 router ID, interfaces Routing for Networks: Routing on Interfaces Configured Explicitly (Area 0): explicitly configured to Loopback0 advertise OSPF routes, the GigabitEthernet0/0/1 neighbors the router is GigabitEthernet0/0/0 Routing Information Sources: receiving updates from, and Gateway Distance Last Update the default administrative 3.3.3.3 110 00:09:30 distance, which is 110 for 2.2.2.2 110 00:09:58 Distance: (default is 110) OSPF. R1# © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 62 Verify Single-Area OSPFv2 Verify OSPF Process Information The show ip ospf command can also be R1# show ip ospf Routing Process "ospf 10" with ID 1.1.1.1 used to examine the Start time: 00:01:47.390, Time elapsed: 00:12:32.320 OSPFv2 process ID (output omitted) and router ID, as Cisco NSF helper support enabled Reference bandwidth unit is 10000 mbps shown in the Area BACKBONE(0) command output. Number of interfaces in this area is 3 This command Area has no authentication SPF algorithm last executed 00:11:31.231 ago displays the OSPFv2 SPF algorithm executed 4 times area information and Area ranges are the last time the SPF Number of LSA 3. Checksum Sum 0x00E77E Number of opaque link LSA 0. Checksum Sum 0x000000 algorithm was Number of DCbitless LSA 0 Number of indication LSA 0 executed. Number of DoNotAge LSA 0 Flood list length 0 R1# © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 63 Verify Single-Area OSPFv2 Verify OSPF Interface Settings The show ip ospf interface command provides a detailed list for every OSPFv2-enabled interface. Specify an interface to display the settings of just that interface. This command shows the process ID, the local router ID, the type of network, OSPF cost, DR and BDR information on multiaccess links (not shown), and adjacent neighbors. R1# show ip ospf interface GigabitEthernet 0/0/0 GigabitEthernet0/0/0 is up, line protocol is up Internet Address 10.1.1.5/30, Area 0, Attached via Interface Enable Process ID 10, Router ID 1.1.1.1, Network Type POINT_TO_POINT, Cost: 10 Neighbor Count is 1, Adjacent neighbor count is 1 Adjacent with neighbor 2.2.2.2 Suppress hello for 0 neighbor(s) R1# © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 64 Verify Single-Area OSPFv2 Verify OSPF Interface Settings (Cont.) To get a quick summary of OSPFv2-enabled interfaces, use the show ip ospf interface brief command, as shown in the command output. This command is useful for seeing important information including: Interfaces are participating in OSPF Networks that are being advertised (IP Address/Mask) Cost of each link Network state Number of neighbors on each link R1# show ip ospf interface brief Interface PID Area IP Address/Mask Cost State Nbrs F/C Lo0 10 0 10.10.1.1/24 10 P2P 0/0 Gi0/0/1 10 0 10.1.1.14/30 30 P2P 1/1 Gi0/0/0 10 0 10.1.1.5/30 10 P2P 1/1 R1# © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 65 Verify Single-Area OSPFv2 Packet Tracer - Verify Single-Area OSPFv2 In this Packet Tracer, you will complete the following: Identify and verify the status of OSPF neighbors. Determine how the routes are being learned in the network. Explain how the neighbor state is determined. Examine the settings for the OSPF process ID. Add a new LAN into an existing OSPF network and verify connectivity. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 66 2.7 Module Practice and Quiz © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 67 Module Practice and Quiz Packet Tracer - Single-Area OSPFv2 Configuration In this Packet Tracer, you will complete the following: Implement single-area OSPFv2 in both point-to-point and broadcast multiaccess networks. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 68 Module Practice and Quiz Lab - Single-Area OSPFv2 Configuration In this lab, you will complete the following objectives: Build the network and configure basic device settings Configure and verify single-area OSPFv2 for basic operation Optimize and verify the single-area OSPFv2 configuration © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 69 Module Practice and Quiz What Did I Learn In This Module? OSPFv2 is enabled using the router ospf process-id global configuration mode command. The process-id value represents a number between 1 and 65,535 and is selected by the network administrator. An OSPF router ID is a 32-bit value, represented as an IPv4 address. The router ID is used by an OSPF-enabled router to synchronize OSPF databases and participate in the election of the DR and BDR. Cisco routers derive the router ID based on one of three criteria, in this order: 1) Router ID is explicitly configured using the OSPF router-id rid router configuration mode command, 2) the router chooses the highest IPv4 address of any of configured loopback interfaces or 3) the router chooses the highest active IPv4 address of any of its physical interfaces. The basic syntax for the network command is network network-address wildcard-mask area area- id. Any interfaces on a router that match the network address in the network command can send and receive OSPF packets. When configuring single-area OSPFv2, the network command must be configured with the same area-id value on all routers. The wildcard mask is typically the inverse of the subnet mask configured on that interface, but could also be a quad zero wildcard mask, which would specify the exact interface. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 70 Module Practice and Quiz What Did I Learn In This Module? (Cont.) To configure OSPF directly on the interface, use the ip ospf interface configuration mode command. The syntax is ip ospf process-id area area-id. Use the passive-interface router configuration mode command to stop transmitting routing messages through a router interface, but still allow that network to be advertised to other routers. The DR/ BDR election process is unnecessary as there can only be two routers on the point-to- point network between R1 and R2. Use the interface configuration command ip ospf network point-to-point on all interfaces where you want to disable the DR/BDR election process. By default, loopback interfaces are advertised as /32 host routes. To simulate a real LAN, the Loopback 0 interface is configured as a point-to-point network. OSPF Network Types The DR is responsible for collecting and distributing LSAs. The DR uses the multicast IPv4 address 224.0.0.5 which is meant for all OSPF routers. If the DR stops producing Hello packets, the BDR promotes itself and assumes the role of DR. All other routers become a DROTHER. DROTHERs use the multiaccess address 224.0.0.6 (all designated routers) to send OSPF packets to the DR and BDR. Only the DR and BDR listen for 224.0.0.6. To verify the roles of the OSPFv2 router, use the show ip ospf interface command. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 71 Module Practice and Quiz What Did I Learn In This Module? (Cont.) To verify the OSPFv2 adjacencies, use the show ip ospf neighbor command. The state of neighbors in multiaccess networks can be: FULL/DROTHER, FULL/DR. FULL/BDR, or 2- WAY/DROTHER. The OSPF DR and BDR election decision is based on the router with the highest interface priority as the DR. The router with the second highest interface priority is elected as the BDR. If the interface priorities are equal, then the router with the highest router ID is elected the DR. The router with the second highest router ID is the BDR. The interface priority can be configured to be any number between 0 – 255. If the interface priority value is set to 0, that interface cannot be elected as DR nor BDR. The default priority of multiaccess broadcast interfaces is 1. OSPF DR and BDR elections are not pre-emptive. If the DR fails, the BDR is automatically promoted to DR. To set the priority of an interface, use the command ip ospf priority value, where value is 0 to 255. If the value is 0, the router will not become a DR or BDR. If the value is 1 to 255, then the router with the higher priority value will more likely become the DR or BDR on the interface. OSPF uses cost as a metric. A lower cost indicates a better path than a higher cost. The formula used to calculate the OSPF cost is: Cost = reference bandwidth / interface bandwidth. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 72 Module Practice and Quiz What Did I Learn In This Module? (Cont.) Because the OSPF cost value must be an integer, FastEthernet, Gigabit Ethernet, and 10 GigE interfaces share the same cost. To correct this situation, you can adjust the reference bandwidth with the auto-cost reference-bandwidth command on each OSPF router, or manually set the OSPF cost value with the ip ospf cost command. The cost of an OSPF route is the accumulated value from one router to the destination network. OSPF cost values can be manipulated to influence the route chosen by OSPF. To change the cost value report by the local OSPF router to other OSPF routers, use the interface configuration command ip ospf cost value. If the Dead interval expires before the routers receive a Hello packet, OSPF removes that neighbor from its link-state database (LSDB). The router floods the LSDB with information about the down neighbor out all OSPF-enabled interfaces. Cisco uses a default of 4 times the Hello interval or 40 seconds on multiaccess and point-to-point networks. To verify the OSPFv2 interface intervals, use the show ip ospf interface command. OSPFv2 Hello and Dead intervals can be modified manually using the following interface configuration mode commands: ip ospf hello-interval and ip ospf dead-interval. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 73 Module Practice and Quiz What Did I Learn In This Module? (Cont.) In OSPF terminology, the router located between an OSPF routing domain and a non-OSPF network is called the ASBR. To propagate a default route, the ASBR must be configured with a default static route using the ip route 0.0.0.0 0.0.0.0 [next-hop-address | exit-intf] command, and the default-information originate router configuration command. Verify the default route settings on the ASBR using the show ip route command. Additional commands for determining that OSPF is operating as expected include: show ip ospf neighbor, show ip protocols, show ip ospf, and show ip ospf interface. Use the show ip ospf neighbor command to verify that the router has formed an adjacency with its neighboring routers. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 74 Module 3: Network Security Concepts Enterprise Networking, Security, and Automation v7.0 (ENSA) Module Objectives Module Title: Network Security Concepts Module Objective: Explain how vulnerabilities, threats, and exploits can be mitigated to enhance network security. Topic Title Topic Objective Current State of Cybersecurity: Describe the current state of cybersecurity and vectors of data loss. Threat Actors Describe tools used by threat actors to exploit networks. Malware Describe malware types. Common Network Attacks Describe common network attacks. IP Vulnerabilities and Threats Explain how IP vulnerabilities are exploited by threat actors. TCP and UDP Vulnerabilities Explain how TCP and UDP vulnerabilities are exploited by threat actors. IP Services Explain how IP services are exploited by threat actors. Network Security Best Practices Describe best practices for protecting a network. Cryptography Describe common cryptographic processes used to protect data in transit. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 2 © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 3 Ethical Hacking Statement In this module, learners may be exposed to tools and techniques in a “sandboxed”, virtual machine environment to demonstrate various types of cyber attacks. Experimentation with these tools, techniques, and resources is at the discretion of the instructor and local institution. If the learner is considering using attack tools for educational purposes, they should contact their instructor prior to any experimentation. Unauthorized access to data, computer, and network systems is a crime in many jurisdictions and often is accompanied by severe consequences, regardless of the perpetrator’s motivations. It is the learner’s responsibility, as the user of this material, to be cognizant of and compliant with computer use laws. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 4 CIA Triad Control access to critical data Prevent unauthorized disclosure of data Ensure data is not tampered or compromised whether in transit, in use or in storage. Authorized users can get timely and reliable access to resources. https://websitesecuritystore.com/blog/what-is-the-cia-triad/ © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 5 McCumber Cube for Info Security Motion: While in transit Rest: While in storage Use: While being processed Technology: Devices, Products Policies & Practices: Guidelines in the company and organization People: Awareness, Education/Training © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 6 3.1 Current State of Cybersecurity © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 7 Current State of Cybersecurity Current State of Affairs Cyber criminals now have the expertise and tools necessary to take down critical infrastructure and systems. Their tools and techniques continue to evolve. Maintaining a secure network ensures the safety of network users and protects commercial interests. All users should be aware of security terms in the table. Security Terms Description An asset is anything of value to the organization. It includes people, equipment, resources, Assets and data. Vulnerability A vulnerability is a weakness in a system, or its design, that could be exploited by a threat. Threat A threat is a potential danger to a company’s assets, data, or network functionality. Exploit An exploit is a mechanism that takes advantage of a vulnerability. Mitigation is the counter-measure that reduces the likelihood or severity of a potential Mitigation threat or risk. Network security involves multiple mitigation techniques. Risk is the likelihood of a threat to exploit the vulnerability of an asset, with the aim of Risk negatively affecting an organization. Risk is measured using the probability of the occurrence of an event and its consequences. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 8 Current State of Cybersecurity Vectors of Network Attacks An attack vector is a path by which a threat actor can gain access to a server, host, or network. Attack vectors originate from inside or outside the corporate network, as shown in the figure. Internal threats have the potential to cause greater damage than external threats because internal users have direct access to the building and its infrastructure devices. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 9 Current State of Cybersecurity Data Loss Data loss or data exfiltration is when data is intentionally or unintentionally lost, stolen, or leaked to the outside world. The data loss can result in: Brand damage and loss of reputation Loss of competitive advantage Loss of customers Loss of revenue Litigation/legal action resulting in fines and civil penalties Significant cost and effort to notify affected parties and recover from the breach Network security professionals must protect the organization’s data. Various Data Loss Prevention (DLP) controls must be implemented which combine strategic, operational and tactical measures. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 10 Current State of Cybersecurity Data Loss (Cont.) Data Loss Vectors Description Email/Social Intercepted email or IM messages could be captured and reveal confidential information. Networking If the data is not stored using an encryption algorithm, then the thief can retrieve valuable Unencrypted Devices confidential data. Cloud Storage Sensitive data can be lost if access to the cloud is compromised due to weak security Devices settings. One risk is that an employee could perform an unauthorized transfer of data to a USB drive. Removable Media Another risk is that a USB drive containing valuable corporate data could be lost. Hard Copy Confidential data should be shredded when no longer required. Improper Access Passwords or weak passwords which have been compromised can provide a threat actor Control with easy access to corporate data. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 11 3.2 Threat Actors © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 12 Threat Actors The Hacker Hacker is a common term used to describe a threat actor Hacker Type Description These are ethical hackers who use their programming skills for good, ethical, and White Hat Hackers legal purposes. Security vulnerabilities are reported to developers for them to fix before the vulnerabilities can be exploited. These are individuals who commit crimes and do arguably unethical things, but not Gray Hat Hackers for personal gain or to cause damage. Gray hat hackers may disclose a vulnerability to the affected organization after having compromised their network. These are unethical criminals who compromise computer and network security for Black Hat Hackers personal gain, or for malicious reasons, such as attacking networks. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 13 Threat Actors The Evolution of Hackers The table displays modern hacking terms and a brief description of each. Hacking Term Description These are teenagers or inexperienced hackers running existing scripts, tools, and exploits, to Script Kiddies cause harm, but typically not for profit. Vulnerability These are usually gray hat hackers who attempt to discover exploits and report them to Broker vendors, sometimes for prizes or rewards. These are gray hat hackers who publicly protest organizations or governments by posting Hacktivists articles, videos, leaking sensitive information, and performing network attacks. These are black hat hackers who are either self-employed or working for large cybercrime Cyber criminals organizations. These are either white hat or black hat hackers who steal gove

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