CCNA CheatSheet PDF

Contents 1. Introduction - OSI and TCP/IP.......................1 2. Cisco IOS Essentials.....................................2 3. Router Password Recovery..........................3 4. IPv4 Addressing.............................................4 5. IPv6 Addressing................................

Contents 1. Introduction - OSI and TCP/IP.......................1 2. Cisco IOS Essentials.....................................2 3. Router Password Recovery..........................3 4. IPv4 Addressing.............................................4 5. IPv6 Addressing.............................................6 6. Subnetting......................................................7 7. Routing Protocols - EIGRP ….....................10 8. Routing Protocols OSPF.............................12 9. Network Address Translation (NAT)..........14 10. Access Control Lists (ACLs)......................15 11. VLANs and VTP............................................16 12. Ether Channel..............................................17 13. Spanning Tree Protocol..............................18 14. Router Redundancy (VRRP/HSRP)............20 15. Frequently Used Commands......................22 Copyright © 2014 SimulationExams.com * All trademarks are duly recognized * Best printed in landscape mode CCNA Network Simulator CCNA Exam Simulator CCENT Exam Simulator CCNA ICND2 Exam Simulator CCNP BSCI Exam Simulator  Cisco™ CCNA : OSI and TCP/IP OSI MODEL Application : Responsible for identifying and establishing the availability of desired comm partner and verifying sufficient resources exist for comm. Ex: FTP, SMTP TCP/IP MODEL Presentation : Responsible for presenting the data in standard formats. Some Presentation layer standards are JPEG, MPEG, MIDI, PICT, Quick Time, TIFF. Application : Defines TCP/IP application protocols and how host programs interface with transport layer services to use the network. Ex: FTP, SMTP, Telnet Session : Responsible for co-ordinating communication between systems/nodes. Some of the session layer protocols and interfaces: NFS, RPC, SQL, ASP, DNA SCP Transport : Provides communication session management between host computers. Ex: TCP, UDP Transport : Responsible for multiplexing upper-layer applications, session mgmt tearing down of virtual circuits, flow control and to maintain data integrity. Internet : Performs routing of IP datagrams. Network : Responsible for sending packets from the source network to the destination Ex: IP, ARP, ICMP network using routing methods. Routers work at network layer. Datalink : Consists of LLC sublayer and MAC sublayer. LLC handles error control, flow Physical : Controls the hardware devices and media that make flow control, framing etc. MAC handles access to shared media such as ethernet. up the network. Physical : Responsible for ultimate transmission of data over network communications media. Some of the standard interfaces at physical layer are EIA/TIA-232, V.24,V.35, HSSI Port numbers used by TCP/UDP 0-255 : Used for public applications Some important port numbers 255-1023 : Assigned to companies Above 1023 : Used by upper layers to set up sessions with other hosts and by FTP : Port 20-21 Telnet : Port 23 DHCP : Ports 67 and 68 POP3 : Port 110 TCP to use as source and destination addresses. TFTP : Port 69 SMTP : Port 25 DNS : Port 53 HTTP : Port 80 Copyright © 2014 SimulationExams.com * All trademarks are duly recognized * Best printed in landscape mode CCNA Network Simulator CCNA Exam Simulator CCENT Exam Simulator CCNA ICND2 Exam Simulator CCNP BSCI Exam Simulator 1  Cisco™ CCNA : IOS Internal memory components of a cisco router Router Cursor Commands ROM : Memory containing micro-code for basic functions to start and maintain the router. A: Move to the beginning of the command line RAM/DRAM : Stores the running configuration, routing tables, and packet buffers. E: Move to the end of the command line NVRAM : Memory that does not lose information when power is lost. Stores the system’s F: Move forward one character, same as using “Right Arrow” configuration file and the configuration register. B: Move backward one character, same as using “Left Arrow". Flash Memory : Stores the compressed IOS image. P: Repeat Previous command, same as using “Up Arrow” N: Repeat Next (more recent) command, same as using "Down Arrow" Router Default Boot Sequence for Cisco IOS Router boot configuration commands B: Moves to beginning of previous word. F: Moves to beginning of next word. 1. NVRAM 3. TFTP server boot system ROM : boots from system ROM R: Creates new command prompt, followed by all the 2. Flash (sequential) 4. ROM boot system flash : boots characters typed at the last one. IOS from flash memory boot system tftp The router first looks at Startup Config file in NV RAM, if not available, it falls back to Flash, then : boots IOS from a tftp server to TFTP and then to ROM. Configuration Register Command Router modes of operation include Router passwords Router(config)# config-register 0x10x (where that last x is 0-F in hex), when the last x is: 0 = boot into ROM Monitor mode; 1 = boot the ROM IOS; 2 - 15 = look in startup-config file in NVRAM. Mode---------------------------> Prompt Enable password user exec---------------------> Router> Console password Privileged----------------------> Router # Enable Secret Cisco router configurable locations global config------------------> Router(config)# Virtual terminal password (vty) Interface config--------------> Router(config-if)# Auxiliary password Console port, Virtual Terminals (vty), Auxiliary port, TFTP server and Network management station Three ways router learns to forward packets More info To enable the Cisco IOS to forward packets destined for 1. Static routes : Configured by the administrator manually. Syntax : ip route obscure subnets of directly connected networks onto the best Ex: R1(config)#ip route 192.168.200.0 255.255.255.0 192.168.1.2 route, use "ip classless" command. 2. Default routes : This is used when a route is not known or is infeasible. Syntax : ip route 0.0.0.0 0.0.0.0 Ex: R1(config)#ip route 0.0.0.0 0.0.0.0 192.168.1.2 3. Dynamic routes : In dynamic routing, the routing tables are automatically updated. By default, Cisco routers support 5 simultaneous telnet sessions. Dynamic routing uses broadcasts and multicasts to communicate with other routers. This number can be configured using IOS commands. Copyright © 2014 SimulationExams.com * All trademarks are duly recognized * Best printed in landscape mode CCNA Network Simulator CCNA Exam Simulator CCENT Exam Simulator CCNA ICND2 Exam Simulator CCNP BSCI Exam Simulator 2  Cisco™ CCNA : Password Recovery Procedure 1 Procedure 2 Complete these steps in order to recover your password: Complete these steps in order to recover your password: 1. Attach a terminal or PC with terminal emulation to the console port of the router and 1. Shut down the router. set terminal settings to 9600 baud rate, No parity, 8 data bits, 1 stop bit, No flow 2. Remove the compact flash that is at the back of the router. control. 3. Power on the router. The configuration register is usually set to 0x2102 or 0x102. If you can no longer 4. Once the Rommon1> prompt appears, enter this command: access the router you can safely assume that your configuration register is set to confreg 0x2142 0x2102. 5. Insert the compact flash. 2. Use the power switch in order to turn off the router, and then turn the router back on. 6. Type reset. 3. Press Break on the terminal keyboard within 60 seconds of power up in order to put 7. When you are prompted to enter the initial configuration, type No, and press Enter. the router into ROMmon. 8. At the Router> prompt, type enable. 4. Type confreg 0x2142 at the rommon 1> prompt in order to boot from Flash. This step 9. At the Router# prompt, enter the configure memory command, and press Enter in bypasses the startup configuration where the passwords are stored. order to copy the startup configuration to the running configuration. 5. Type reset at the rommon 2> prompt. 10. Use the config t command in order to enter global configuration mode. The router reboots, but ignores the saved configuration. 11. Use this command in order to create a new user name and password: 6. Type no after each setup question, or press Ctrl-C in order to skip the initial setup router(config)#username cisco password cisco procedure. 12. Use this command in order to change the boot statement: 7. Type enable at the Router> prompt. config-register 0x2102 You are in enable mode and should see the Router# prompt. 13. Use this commnd in order to save the configuration: 8. Type configure memory or copy startup-config running-config in order to copy write memory the nonvolatile RAM (NVRAM) into memory. 9. Type configure terminal. Reload the router, and then use the new user name and password to log in to the The router(config)# prompt appears. router. 10. Type enable secret in order to change the enable secret password. For example: router(config)#enable secret cisco 11. Issue the no shutdown command on every interface that you use. 12. Type write memory or copy running-config startup-config in order to commit the changes. Note : The given procedures are generic in nature, and for exact sequence of steps, please refer to product manual. Copyright © 2014 SimulationExams.com * All trademarks are duly recognized * Best printed in landscape mode CCNA Network Simulator CCNA Exam Simulator CCENT Exam Simulator CCNA ICND2 Exam Simulator CCNP BSCI Exam Simulator 3  Cisco™ CCNA : IPv4 Addressing Converting Binary to Decimal Converting Decimal to Binary Binary is a base 2 system with only two numbers 0 or 1. Decimal is a Base 10 system with 10 possible values (0 to 9) The weightage of binary digits from right most bit position to the left most bit position is given below. To convert decimal to binary, simply divide the decimal value by 2 and then write down the remainder, repeat this process until you cannot divide by 2 anymore. For example, take the decimal value 157: 157 ÷ 2 = 78 with a remainder of 1 78 ÷ 2 = 39 with a remainder of 0 39 ÷ 2 = 19 with a remainder of 1 19 ÷ 2 = 9 with a remainder of 1 9÷2=4 with a remainder of 1 4÷2=2 with a remainder of 0 2÷2=1 with a remainder of 0 1÷2=0 with a remainder of 1 Example : To convert, write this remainder first-----------> Convert 10011101 into a decimal value. There are eight bits in the binary number. The decimal value for each bit position is given below: Next write down the value of the remainders from bottom to top (in other words write down the bottom remainder first and work your way up the list) which gives: 10011101 = 157 To convert, you simply take a value from the top row wherever there is a 1 below, and then add the values together. i.e, 1*27 + 0*26 + 0*25 + 1*24 + 1*23 + 1*22 + 0*21 + 1*20 = 128 + 0 + 0 + 16 + 8 + 4 + 0 + 1 = 157 (decimal value) Copyright © 2014 SimulationExams.com * All trademarks are duly recognized * Best printed in landscape mode CCNA Network Simulator CCNA Exam Simulator CCENT Exam Simulator CCNA ICND2 Exam Simulator CCNP BSCI Exam Simulator 4  Cisco™ CCNA : IPv4 Addressing IP Address Intro IP Address Classes ( Public IP range) 1. An IP address (32 bit number, 4 bytes) consists of four octets seperated Class Format Leading-bit-pattern Network-addr-range Max-netw Max-hosts by dots. A N.H.H.H 0 0-126 127 16,777,214 The octet is a binary number of eight digits, which equals the decimal numbers from 0 to 255. B N.N.H.H 10 128-191 16,384 65,534 C N.N.N.H 110 192 -223 2,097,152 254 Class D addresses are used for multicasting, they begin with “1110” and the addr range is 224-239. Class E addresses are reserved addresses that begin with “11110” and the range is 240-254. 2. The internet protocol defines the special network address 127.0.0.1 as a Private addr range : Class A : 10.0.0.0 to 10.255.255.255, Class B : 172.16.0.0 to 172.31.255.255, local loopback address. Class C : 192.168.0.0 to 192.168.255.255 IPV4 Header Subnet Mask and CIDR notation A Subnet mask is a 32-bit number that masks an IP address, and divides the IP address into network address and host address. Subnet Mask is made by setting network bits to all "1"s and setting host bits to all "0"s. Default Subnet Masks Class A : 255.0.0.0, Class B : 255.255.0.0, Class C : 255.255.255.0 CIDR Notation : Classless Inter Domain Routing (CIDR) is a method for assigning IP addresses without using the standard IP address classes like Class A, Class B or Class C. In CIDR notation, an IP address is represented as A.B.C.D /n, where "/n" is called the IP prefix or network prefix. The IP prefix identifies the number of significant bits used to identify a network. Ex: 216.3.128.12, with subnet mask of 255.255.255.128 may be written as 216.3.128.12/25 using CIDR Notation. Copyright © 2014 SimulationExams.com * All trademarks are duly recognized * Best printed in landscape mode CCNA Network Simulator CCNA Exam Simulator CCENT Exam Simulator CCNA ICND2 Exam Simulator CCNP BSCI Exam Simulator 5  Cisco™ CCNA : IPv6 Addressing IPv6 : Points to Remember IPv6 Header 1. IPv6 address is 128 bits in length represented in hexadecimal 2. IPv6 Loopback address is 0:0:0:0:0:0:0:1, also expressed as ::1. 3. IPv6 reserves two special addresses. They are 0:0:0:0:0:0:0:0 and 0:0:0:0:0:0:0:1. 4. Three transition strategies for migration from ipv6 to ipv4 are dual stacking, 6-to-4 tunneling and NAT-PT IPv6 Addressing Version (4 bits) : IP version number (6) IPv6 address consists of 8 groups of four hexadecimal digits separated by colons and which mainly consists of 3 segments called Global Prefix which is of 48 bits, subnet part with 16 bits and Interface ID called as Host Traffic Class (8 bits) : Used for QoS part with 64 bits. Flow Label (20 bits) : Used for packet labelling The first 3 octets constitute Global Prefix, the fourth octet constitute subnet part and the last four form the Interface ID. Payload Length (16 bits) : Length of the IPv6 payload Next Header (8 bits) : Identifies the type of header following the IPv6 header Hop Limit (8 bits) : Number of hops until the packet gets discarded. Source Address (128 bits) : Source IP address Rules : a) One set of 0's in the address can be replaced by :: but this can be done only once b) One or any number of consecutive groups of 0 value can be replaced with two colons (::) Destination Address (128 bits) : Destination IP address EUI-64 Format IPv6 Communication Types IPv6 Address Scopes MAC to EUI-64 conversion inserts hex “FFFE” in the middle of a MAC addr, Then flips the U/L bit to 1, in order to create a 64-bit interface ID from a 48-bit Mac address. Unicast : used for one-to-one communication. There are 3 types of unicast addresses namely ::/0----------------> Default Route global, unique-local and link-local ::/128------------> Unspecified ::1/128-----------> Loopback Multicast : used for one-to-many communication FC00::/7---------> Unique Local Unicast IPv6 multicast address begins with "FF" FE80::/10--------> Link-Local Unicast FEC0::/10-------> Site-Local Unicast Anycast : used for one-to-one-of-many FF00::/8----------> Multicast communication Copyright © 2014 SimulationExams.com * All trademarks are duly recognized * Best printed in landscape mode CCNA Network Simulator CCNA Exam Simulator CCENT Exam Simulator CCNA ICND2 Exam Simulator CCNP BSCI Exam Simulator 6  Cisco™ CCNA : Subnetting Requirement for IPv4 Subnetting Subnetting Scenarios 1. Efficient use of available IP address space The subnetting scenarios may broadly be divided in to two categories: 2. Network traffic isolation 1. Optimize for a given number of hosts 3. Improved security 2. Optimize for a given number of subnets 4. Limiting broadcast messages Finally, determine the host address range for each available subnet. Subnetting Scenario Question 1 You want X number of subnets, what is the subnet mask ? (Assume we need 10 subnets, i.e, X=10) Tip : Convert X to binary, determine how many low order bits need to make the number, that many bits is number of high order bits that make up your subnet mask, convert high order bits to decimal value. Solution : Consider the Class C address – N.N.N.H where N is the Network portion and H is the host portion. Host Portion is as shown -----> Step 1: Convert 10 to binary. Binary equivalent of 10 is as shown ---------> Step 2: Number of low order bits required to make the number is 4 (from the figure shown above) Step 3: Therefore 4 high-order bits make up the subnet mask, i.e, 128, 64, 32, 16 Add 4 high order bits to create subnet mask i.e. 128+64+32+16=240 (11110000). The subnet mask is 255.255.255.255.240 255.255.255.240 is represented as --------> Copyright © 2014 SimulationExams.com * All trademarks are duly recognized * Best printed in landscape mode CCNA Network Simulator CCNA Exam Simulator CCENT Exam Simulator CCNA ICND2 Exam Simulator CCNP BSCI Exam Simulator 7  Cisco™ CCNA : Subnetting Subnetting Scenario Question 3 Determine the range of valid IP Addresses for an X subnet mask ? (Assume X value to be 240 in this case) Tip : Convert X to binary and determine the decimal value of lowest high order bit, start the range of addresses at that value, and increment the range by that value.. Solution : Step 1: Convert 240 to binary. Binary equivalent of 240 is as shown ---------> Step 2: The decimal value of lowest high order bit is 16 (24) as seen from the figure above. Therefore, this number becomes the increment value to determine the IP address ranges. Subnet Mask: 255.255.255.240 Subnet Bits: 28 Host Bits: 4 Number of Subnets: 16 Hosts per Subnet: 14 The range of addresses for the given mask is as shown ------> Note: All zeros and all ones host addresses cannot be used. Copyright © 2014 SimulationExams.com * All trademarks are duly recognized * Best printed in landscape mode CCNA Network Simulator CCNA Exam Simulator CCENT Exam Simulator CCNA ICND2 Exam Simulator CCNP BSCI Exam Simulator 8  Cisco™ CCNA : Subnetting Subnetting Scenario Question 2 How many subnet bits are required for X number of hosts ? (Assume X value to be 5 in this case) Tip : Convert X (for the subnets) to binary, determine the number of bits needed for the host portion, additionally determine the subnet mask from the remaining bits, using formula 2ⁿ, find the relevant number of subnets in this scenario.. Solution : Step 1: Consider the Class C address N.N.N.H, where H is the host portion whose binary and decimal representation is as shown ----> Convert 5 to binary. Binary equivalent of 5 is as shown ---------> Step 2: As shown in the figure above, the number of bits needed for the host portion are 3. Therefore, 2bits-2=23-2=6 (6>5) 3 bits are required for the host portion for 5 hosts. Step 3 (Additional): To know the subnet mask , add the decimal value of the remaining 5 bits i.e, (128+64+32+16+8) = 248 Subnet Mask is 255.255.255.248 (11111111.11111111.11111111.11111000) Number of subnet bits: 29, here 5 bits are used from the host portion of our subnet mask Therefore number of subnets required is (2n), where 'n' is the number of bits being used from the host portion of our subnet mask i.e. 5 Therefore, 25=32 is the number of subnets Copyright © 2014 SimulationExams.com * All trademarks are duly recognized * Best printed in landscape mode CCNA Network Simulator CCNA Exam Simulator CCENT Exam Simulator CCNA ICND2 Exam Simulator CCNP BSCI Exam Simulator 9  Cisco™ CCNA : EIGRP EIGRP (Enhanced Interior Gateway Protocol) Important terms used in EIGRP Routing metrics used by IGRP Successor: A route (or routes) selected as the primary route(s) used to Bandwidth: This is represents the maximum throughput of a link. transport packets to reach destination. Note that successor entries are kept in the routing table of the router. MTU (Maximum Transmission Unit): This is the maximum message length that is acceptable to all links on the path. The larger MTU means faster transmission of packets. Feasible successor: A route (or routes) selected as backup route(s) used to transport packets to reach destination. Note that feasible successor entries Reliability: This is a measurement of reliability of a network link. It is assigned by the are kept in the topology table of a router. administrator or can be calculated by using protocol statistics. DUAL (Diffusing Update Algorithm): Enhanced IGRP uses DUAL algorithm to Delay: This is affected by the band width and queuing delay. calculate the best route to a destination Load: Load is based among many things, CPU usage, packets processed per sec Important Command in EIGRP Important Features of EIGRP 1. Show ip eigrp topology : To display entries in the EIGRP topology table, use the show ip 1. Unlike RIP and IGRP, EIGRP updates are not periodic. EIGRP updates are sent only when eigrp topology command in EXEC mode. there is a topological change in the network. 2. show ip eigrp neighbours : To display the neighbors discovered by EIGRP, use the 2. In EIGRP, the router doing the summarization will build a route to null0 for the summarized show ip eigrp neighbors command in EXEC mode. It shows when neighbors become address. This ensures that the packets that are not destined for any network are routed active and inactive. The neighbor parameters displayed include Address, Interface, to null and thus dropped. Holdtime, Uptime, Q, Seq Num, SRTT, and RTO. 3. EIGRP provides the option of disabling route summarization.The command no 3. show ip route eigrp : Displays the EIGRP routes installed in the route table. auto-summary can be used for this purpose. This option is not available in RIP and IGRP. 4. Show ip eigrp interface: Use the show ip eigrp interfaces command to determine on which 4. You can summarize routes in EIGRP at any arbitrary bit boundary interfaces EIGRP is active, and to find out information about EIGRP relating to those interfaces. The details shown include interfaces on which EIGRP is configured, numbered of directly connected EIGRP neighbours on each interface, Mean SRTT, etc. Copyright © 2014 SimulationExams.com * All trademarks are duly recognized * Best printed in landscape mode CCNA Network Simulator CCNA Exam Simulator CCENT Exam Simulator CCNA ICND2 Exam Simulator CCNP BSCI Exam Simulator 10  CiscoTM CCNA : EIGRP Packet types used by EIGRP when communicating with its neighboring EIGRP routers Different Tables Used by EIGRP 1. Hello Packets - EIGRP sends Hello packets once it has been enabled on a router for a 1. Neighbor table: The neighbor table stores information about neighboring EIGRP routers: network. These messages are used to identify neighbors and once identified, serve or a. Network address (IP) function as a keep alive mechanism between neighbors. EIGRP Hello packets are sent to b. Connected interface the link local Multicast group address 224.0.0.10.Hello packets sent by EIGRP do not require c. Holdtime - how long the router will wait to receive another HELLO before dropping an Acknowledgment to be sent confirming that they were received. the neighbor; default = 3 * hello timer d. Uptime - how long the neighborship has been established 2. Acknowledgment Packets - An EIGRP Acknowledgment (ACK) packet is simply an EIGRP e. Sequence numbers Hello packet that contains no data. Acknowledgment packets are used by EIGRP to confirm f. Retransmission Timeout (RTO) - how long the router will wait for an ack before retransmitting reliable delivery of EIGRP packets. ACKs are always sent to a Unicast address, which is the packet; calculated by SRTT the source address of the sender. g. Smooth Round Trip Time (SRTT) - time it takes for an ack to be received once a packet has been transmitted 3. Update Packets - EIGRP Update packets are used to convey reachability of destinations. Update h. Queue count - number of packets waiting in queue; a high count indicates line congestion packets contain EIGRP routing updates. When a new neighbor is discovered, Update packets are sent via Unicast to the neighbor which the can build up its EIGRP Topology Table. It is important to know that Update packets are always transmitted reliably and always require explicit 2. Topology table: It contains only the aggregation of the routing tables gathered from all Acknowledgment. directly connected neighbors (not the entire network!). This table contains a list of destination networks in the EIGRP- routed network together with their respective metrics. Also for every 4. Query Packet - EIGRP Query packets are Multicast and are used to reliably request routing destination, a successor and a feasible successor are identified and stored in the table if they information. EIGRP Query packets are sent to neighbors when a route is not available and the exist. Every destination in the topology table can be marked either as "Passive", which is the router needs to ask about the status of the route for fast convergence. If the router that sends state when the routing has stabilized and the router knows the route to the destination, or out a Query does not receive a response from any of its neighbors, it resends the Query "Active" when the topology has changed and the router is in the process of (actively) as a Unicast packet to the non-responsive neighbor(s). If no response is received in 16 attempts, updating its route to that destination. the EIGRP neighbor relationship is reset. 5. Reply Packets - EIGRP Reply packets are sent in response to Query packets. The Reply packets 3. Routing table: Stores the actual routes to all destinations; the routing table is populated from the are used to reliably respond to a Query packet. Reply packets are Unicast to the originator of the topology table with every destination network that has its successor and optionally feasible Query. successor identified (if unequal-cost load-balancing is enabled using the variance command) The successors and feasible successors serve as the next hop routers for these destinations. 6. Request Packets - Request packets are used to get specific information from one or more neighbors and are used in route server applications. These packet types can be sent either via Multicast or Unicast, but are always transmitted unreliably. Copyright © 2014 SimulationExams.com * All trademarks are duly recognized * Best printed in landscape mode CCNA Network Simulator CCNA Exam Simulator CCENT Exam Simulator CCNA ICND2 Exam Simulator CCNP BSCI Exam Simulator 11  Cisco™ CCNA : OSPF OSPF router ID determination OSPF Priority OSPF and OSPF Area OSPF is a link state technology that uses Dijkstra algorithm to compute routing 1. Use the address configured by the ospf router-id command The ip ospf priority command is information. used to set manually which router 2. Use the highest numbered IP address of a loopback becomes the DR. The range is 0- An OSPF area is a collection of networks and routers that have the same area interface 255 and the default is 1. 0 means identification.OSPF process identifier is locally significant. it will never be DR or BDR. 3. Use the highest IP address of any physical interface 4. If no interface exists, set the router-ID to 0.0.0.0 DR and BDR Election When two or more routers are contending to be a DR (designated Router) on a network segment, the router with the highest OSPF priority will become the DR for that segment. The same process is repeated for the BDR. In case of a tie, the router with the highest RID will win. OSPF Area Types Router Types Standard Area : Default OSPF area type Internal Router : All interfaces reside within the same area Stub Area : External link (type 5) LSAs are replaced with a default route Backbone Router : A router with an interface in area 0 (the backbone) Totally Stubby Area : Type 3, 4, and 5 LSAs are replaced with a default route Area Border Router (ABR) : Connects two or more areas Not So Stubby Area (NSSA) : A stub area containing an ASBR; type 5 LSAs are AS Boundary Router (ASBR) : Connects to additional routing domains; typically located in converted to type 7 within the area the backbone Copyright © 2014 SimulationExams.com * All trademarks are duly recognized * Best printed in landscape mode CCNA Network Simulator CCNA Exam Simulator CCENT Exam Simulator CCNA ICND2 Exam Simulator CCNP BSCI Exam Simulator 12  Cisco™ CCNA : OSPF OSPF LSA Types LSAs used by different OSPF Areas a. LSA 1 (Router LSA): Generated by all routers in an areato describe their directly attached links (Intra-area routes).These do not leave the area. b. LSA 2 (Network LSA): Generated by the DR of a broadcast or Nonbroadcast segment to a. Area backbone LSAs: The LSAs generated by Area Backbone Routers are LSA1, describe the neighbors connected to the segment. These do not leave the area. LSA2, LSA3, LSA4, and LSA5. Note that LSA6 is not supported by Cisco, and c. LSA 3 (Summary LSA): Generated by the ABR to describe a route to neighbors outside the LSA7 is generated by NSSA router. area(Inter-area routes). d. LSA 4 (Summary LSA): Generated by the ABR to describe a route to an ASBR to neighbors outside the area. b. Stub area LSAs: The Stub area router generates LSA types 1, 2, and 3. i.e. e. LSA 5 (External LSA): Generated by ASBR to describe routes redistributed into the area. Router LSA, Network LSA, and Summary LSA. These routes appear as E1 or E2 in the routing table. E2 (default) uses a static cost Throughout the OSPF domain as it only takes the cost into account that is reported at redistribution. E1 uses a cumulative cost of the cost reported into the OSPF domain at c. Totally Stubby LSAs: The Totally Stubby area routers generate LSA types 1 and 2 Redistribution plus the local cost to the ASBR. NSSA LSAs: A NSSA (Not So Stubby Area) router generates LSA types 1, 2, and 7. f. LSA 6 (Multicast LSA): Not supported on Cisco routers. LSA 7 is translated into LSA 5 as it leaves the NSSA g. LSA 7 (NSSA External LSA): Generated by an ASBR inside a NSSA to describe routes redistributed into the NSSA. LSA 7 is translated into LSA 5 as it leaves the NSSA. These routes appear as N1 or N2 in the ip routing table inside the NSSA. Much like LSA 5 N2 is a static cost while N1 is a cumulative cost that includes the cost up to the ASBR. Important Features of Stub Area Default Route Advertisement in OSPF 1. A stub area reduces the size of the link-state database to be maintained in an area,which in turn result in less overhead in terms of memory capacity, computational power, and convergence time. A default route can be advertised into OSPF domain by an ASBR 2. The routing in Stub and totally Stubby areas is based on default gateway. router in one of two ways: A default route (0.0.0.0) needs to be configured to route traffic outside the area. 3. The stub areas suited for Hub-Spoke topology. 1.By using “default-information originate” command: This command 4. Area 0 is not configured as Stubby or totally Stubby. This is because stub areas can be used when there is a default route(0.0.0.0/0) already existing. are configured mainly to avoid carrying external routes, whereas Area 0 carries This command will advertise a default route into OSPF domain. external routes. 2. By using “default-information originate always” command: This command can be used when there is a default route (0.0.0.0/0) is External Routes present or not. This command is particularly useful when the default route is not consistent. An inconsistent default route may The cost of external route depends on the configuration of ASBR. result in flippingof the route advertised into the OSPF domain, There are two external packet types possible. resulting in instability of the OSPF domain routing information. 1. Type 1 (E1) - Here the metric is calculated by adding the external cost to the internal Therefore,it is recommended to use “always” keyword. cost of each link that the packet crosses. 2. Type 2 (E2) - This type of packet will only have the external cost assigned, irrespective of where in the area it crosses. Type 2 packets are preferred over Type1packets unless there are two same cost routes existing to the destination. Copyright © 2014 SimulationExams.com * All trademarks are duly recognized * Best printed in landscape mode CCNA Network Simulator CCNA Exam Simulator CCENT Exam Simulator CCNA ICND2 Exam Simulator CCNP BSCI Exam Simulator 13  Cisco™ CCNA : NAT Address Classification Static NAT Inside Local : An actual address assigned to an inside host Maps an unregistered IP address to registered IP (globally unique) addresses on one-to-one basis. Inside Global : An inside address seen from the outside The command, ip nat inside source static configures address translation for static NAT. Outside Global : An actual address assigned to an outside host Outside Local : An outside address seen from the inside Dynamic NAT Maps an unregistered IP address to a registered (globally unique) IP address from a group of registered NAT Pool : A pool of IP addresses to be used as inside global or (globally unique) IP addresses. outside local addresses in translations The command, ip nat inside source list pool is used to map the access-list to the IP NAT pool during the configuration of Dynamic NAT. Overloading Configuring NAT A special case of dynamic NAT that maps multiple unregistered IP addresses to a single registered (globally unique) IP address by using different port numbers. Dynamic NAT with overloading is also known also as PAT (Port Address Translation). When configuring NAT, NAT should be enabled on at least one inside and one outside interface. Overlapping 1. The command for enabling NAT on inside interface is: R1(config-if)#ip nat inside This occurs when your internal IP addresses belong to global IP address range that belong to another network. 2. The command for enabling NAT on the outside interface is: Defining an IP NAT Pool R1(config-if)#ip nat outside Remember to enter into appropriate configuration modes 1. Defining an IP NAT pool for the inside network using the command: before entering the commands. ip nat pool {netmask | prefix-length } [type- rotary] Ex: ip nat pool pool1 200.200.200.3 200.200.200.4 netmask 255.255.255.0 Usually, the inside NAT will be configured on an Ethernet interface, whereas the outside NAT is configured on a Note that type-rotary is optional command. It indicates that the IP address range in the address pool identifies serial interface. hosts among which TCP load is distributed. 2. Mapping the access-list to the IP NAT pool by using the command: ip nat inside source list pool Ex: ip nat inside source list 1 pool pool1 Copyright © 2014 SimulationExams.com * All trademarks are duly recognized * Best printed in landscape mode CCNA Network Simulator CCNA Exam Simulator CCENT Exam Simulator CCNA ICND2 Exam Simulator CCNP BSCI Exam Simulator 14  Cisco™ CCNA : Access-Lists Wild Card Masking Access Lists IP access lists are a sequential list of permit and deny conditions that apply to IP addresses or upper Wild card masking is used to permit or deny a group of addresses. layer protocols. Access Control Lists are used in routers to identify and control traffic. For example, if we have a source address 185.54.13.2 and want all the hosts on the last octet to be considered, we use a wild card mask, 185.54.13.255. The 32 bit wildcard mask consists of 1’s and 0’s 1 = ignore this bit Types of IP Access Lists 0 = check this bit Purpose of Access Lists 1. Controlling traffic through a router, and Standard IP Access Lists Special Case: Host 185.54.13.2 is same as 185.54.13.2 with a wild card 2. Controlling VTY access to a router’s VTY Extended IP Access Lists mask of 0.0.0.0, considers only specified IP. ports Named Access Lists Any is equivalent to saying 0.0.0.0 with a wild card mask of 3. Filter incoming and outgoing packets 255.255.255.255. This means none of the bits really matter. All IP 4. Restrict contents of routing updates addresses need to be considered for meeting the criteria. 5. Trigger dial-on-demand routing (DDR) calls Standard Access List Extended Access Lists and Named Access Lists 1. These have the format, access-list [number] [permit or deny] [source_address] Extended Access lists have the format, Ex: access-list 1 permit 192.168.2.0 0.0.0.255 access-list {number}{permit or deny} {protocol} {source}source-wildcard [operator 2. Place standard access lists as near the destination as possible and extended access lists [port]]{destination} destination-wildcard [operator [port]] as close to the source as possible. With extended IP access lists, we can act on any of the following: 3. Access lists have an implicit deny at the end of them automatically. Because of this, an - Source address - Port information (WWW, DNS, FTP, etc.) access list should have at least one permit statement in it; otherwise the access list will - Destination address block all remaining traffic. - IP protocol (TCP, ICMP, UDP, etc.) 4. Access lists applied to interfaces default to outbound if no direction is specified. Ex: access-list 101 permit icmp host 192.168.3.2 any Named Access lists have the format, ip access-list {standard /extended} name Ex: ip access-list extended denyping Permitted numbers for access-lists 1-99: IP standard access list 100-199: IP extended access list 800-899: IPX standard access list 1000-1099: IPX SAP access list 1100-1199: Extended 48-bit MAC address access list 900-999: IPX extended access list Copyright © 2014 SimulationExams.com * All trademarks are duly recognized * Best printed in landscape mode CCNA Network Simulator CCNA Exam Simulator CCENT Exam Simulator CCNA ICND2 Exam Simulator CCNP BSCI Exam Simulator 15  Cisco™ CCNA : VLANs and VTP VLANs – Points to Remember VTP – Points to Remember 1. VTP is a Layer 2 messaging protocol. It carries configuration information throughout a single domain 1. VLAN 1 is the management VLAN. 2. VTP Modes are 2. Static VLAN : VLAN is statically assigned to the physical port and never changes. Server : Create, modify, or delete VLANs (This is the deafult vtp mode on a switch) 3. Dynamic VLAN : VMPS automatically assigns VLAN based on MAC Client : Can't create, change, or delete VLANs 4. Access Link : An access link can carry only one VLAN (used between host and switch port) Transparent : Used when a switch is not required to participate in VTP, but only pass 5. Trunk Link : A trunk link can carry multiple VLANs. Used to connect to other switches, the information to other switches routers, or servers 3. VTP domain is common to all switches participating in VTP 6. Two types of Trunk framing: ISL (Cisco only) and 802.1.q 4. Pruning is a technique where in VLANs not having any access ports on an end switch 7. Trunk links can carry 1 to 1005 VLANs are removed from the trunk to reduce flooded traffic 8. Switchport modes are trunk, dynamic desirable, dynamic auto, access. 5. Configuration revision number is a 32-bit number that indicates the level of revision for a VTP packet. Each time the VTP device undergoes a VLAN change, the config revision is incremented by one. VTP Configuration VLAN configuration Creating VLANs SW1#vlan database Access Port configuration SW1(vlan)#vtp mode (Server/Client/Transparent) SW1#vlan database SW1(config-if)#switchport mode access SW1(vlan)#vtp domain SW1(vlan)#vlan 10 name firstvlan SW1(config-if)#switchport access vlan 10 SW1(vlan)#vtp password SW1(vlan)#vlan 20 name secondvlan SW1(config-if)#switchport access vlan 20 SW1(vlan)#vtp pruning Access port config to a range of interfaces Trunk Port configuration Troubleshooting commands SW1(config)#interface range fa 0/2 - 5 1. show vlan SW1(config-if)#switchport access vlan 10 SW1(config-if)#switchport mode trunk SW1(config)#interface range fa 0/6 - 10 2. show vlan-membership SW1(config-if)#switchport trunk encapsulation dot1q SW1(config-if)#switchport access vlan 20 3. show vtp status 4. show interfaces trunk 5. show interface switchport Copyright © 2014 SimulationExams.com * All trademarks are duly recognized * Best printed in landscape mode CCNA Network Simulator CCNA Exam Simulator CCENT Exam Simulator CCNA ICND2 Exam Simulator CCNP BSCI Exam Simulator 14  Cisco™ CCNA : EtherChannel EtherChannel EtherChannel is a port link aggregation technology used primarily on Cisco Important Features of Bundled Ports Using EtherChannel networking devices.It allows grouping of several physical Ethernet links to create one logical Ethernet link for the purpose of providing fault-tolerance 1. EtherChannel can support from two to 8 links to be bundled into one logical link. and high-speed links between switches, routers and servers. Therefore, if Gigabit Ethernet links are bundled, 8 links represents 8 Gbps of one-way bandwidth, and 16 Gbps for full-duplex operation. 2. The bundled ports must have identical Spanning Tree settings Features of EtherChannel that is running PagP 3. The bundled ports must have the same speed, duplex, and Ethernet media. 4. The bundled ports must belong to the same VLAN if not used as VLAN trunk. 1. PAgP helps in the automatic creation of Fast EtherChannel. 5. If the bundled ports represent a VLAN trunk, then they must have same native 2. PAgP does not group ports configured for dynamic VLANs. PagP requires VLAN,and each port should have same set of VLANs in the trunk. that all ports in a channel must belong to the same VLAN or should be 6. The EtherChannel also provides link redundancy. If one of the bundled links configured as trunk ports. fail,the traffic through the failed link is distributed to other working links in the 3. PAgP does not group ports that work at different speeds or port duplexes. channel.The failover is transparent to the end user. Similarly traffic again flows 4. The load distribution algorithm in EtherChannel can use source IP, through the restored link, as and when a link is restored. destination IP, a combination of source and destination IPs, Source MAC, 7. Note that the load balancing can be done based on source IP, destination IP, destination MAC, or TCP.UDP port numbers for decision process. If there both source and destination IP (XOR), source and destination MAC are only two links in the EtherChannel, only 1 bit in the IP are required. addresses or TCP/UDP port numbers. If there are 4 links in the EtherChannel, 2 bits are required.An XOR on 2 bits can have 4 possible outcomes. Similarly,for an 8 link EtherChannel, 3 bits are required.Conventionally, rightmost bits are always used for XOR operation. PagP (Short for Port Aggregation Protocol) PAgP modes and the corresponding action PagP helps in the automatic creation of Fast EtherChannel links. PagP is 1. ON mode does not send or receive PAgP packets. Therefore, both ends protocol is Cisco proprietary link aggregation protocol used in Cisco switches should be set to ON mode toform an EtherChannel. routers, and servers. 2. Desirable mode tries to ask the other end in order to bring up the EtherChannel. LACP (Short for Link Aggregation Control Protocol) 3. Auto mode participates in the EtherChannel only if the for end asks for LACP is different from PAgP. LACP is a standards based protocol and conforms participation. Two switches in auto mode will not form an EtherChannel. to IEEE standard 802.3ad, whereas PAgP is a Cisco proprietary protocol. Important Commands 1. switch# show etherchannel port Used for verifying the channel negotiation mode of an EtherChannel. 2. Switch# show etherchannel summary Shows each port in the channel along with the status flag. 3. Switch(config)# port-channel load-balance src-ip Will configure load balancing on EtherChannel switch links using source IP address. Copyright © 2014 SimulationExams.com * All trademarks are duly recognized * Best printed in landscape mode CCNA Network Simulator CCNA Exam Simulator CCENT Exam Simulator CCNA ICND2 Exam Simulator CCNP BSCI Exam Simulator 17  CiscoTM CCNA : Spanning Tree Protocol STP – Points to Remember STP Port Roles 1. Root : A bridge can have only one root port. The root port is the port that leads to the root 1. STP is a layer 2 protocol that runs on switches and bridges, the purpose of STP is to remove bridge. All bridges except the root bridge will have a root port. the root port is in the STP switching loops. By default, STP is enabled on cisco switches. forwarding state. 2. All switches participating in STP exchange info with other switches in the network 2. Designated : One designated port is elected per link (segment). The designated port is Through messages known as BPDUs (Sent out at a frequency of 2 sec on every port) the port closest to the root bridge. Each designated port is in the STP forwarding state 3. STP port states are Blocked, Listen, Learn, Forward, Disabled 3. Alternate : Alternate ports lead to the root bridge, but are not root ports. The alternate 4. The command “show spanning-tree” includes the following info ports maintain the STP blocking state. i. VLAN number 4. Backup: This is a special case when two or more ports of the same bridge (switch) are ii. Root bridge priority, MAC address connected together, directly or through shared media. In this case, one port is designated, iii. Bridge timers (Max Age, Hello Time, Forward Delay) and the remaining ports block. The role for this port is backup. Selection Criteria Root Bridge Selection Root Port Selection i. If there are 2 or more paths to reach the Root Bridge, select the bridge port associated with Default Timers The switch with the lowest Bridge ID is chosen as root. the lowest accumulated path cost. OR Bridge ID is a combination of switch priority (32768 by default and the range is 0 to 65535 with ii. If the path cost to reach the root bridge over 2 or more bridge ports is same, then: select the Hello-----------------> 2s increments of 4096) and switch's MAC address neighboring switch with the lowest Switch ID value to reach the Root Bridge OR Forward Delay-----> 15s Max Age-------------> 20s iii. If there are two or more ports on the same bridge with the lowest path cost, then: Designated Bridge Selection * Select the port with the lowest Port Priority value, if you have multiple paths to reach the Root Bridge via same neighbor switch. OR Link Costs * If all the ports are configured with same priority number (32 by default), select the lowest i. In a LAN segment, the bridge with the lowest port number on the switch. path cost to the Root Bridge will be the DB OR Bandwidth Cost Designated Port Selection ii. If there are two bridges in the LAN segment with equal path cost to the Root Bridge, then the 10 Mbps-----------> 100 Bridge with the lowest Bridge ID becomes the i. The switch port (associated with the DB) on the LAN segment with the lowest accumulated path 100 Mbps----------> 19 DB. cost to the Root Bridge will be selected as DP for the given segment. OR 1 Gbps---------------> 4 10 Gbps-------------> 2 ii. If a switch has redundant connections to the network segment, the switch port with the lowest port priority (32 by default) is selected. OR iii. If there is again a tie (it can happen if the priorities of the ports on this switch are the same), then the lowest numbered port on the switch is selected. Copyright © 2014 SimulationExams.com * All trademarks are duly recognized * Best printed in landscape mode CCNA Network Simulator CCNA Exam Simulator CCENT Exam Simulator CCNA ICND2 Exam Simulator CCNP BSCI Exam Simulator 18  CiscoTM CCNA : Spanning Tree Protocol Spanning Tree Port States Protection against sudden loss of BPDUs The ports on a switch with enabled Spanning Tree Protocol (STP) are in one of the following 1.BPDU Skew Detection 2.Root Guard 3.BPDU Guard 4.UDLD 5.Loop Guard five port states. 1. Blocking 2. Listening 3. Learning 4. Forwarding 5.Disabled 1. Root Guard - When configured at the interface level, BPDU Guard shuts the port down as soon as the port receives a superior BPDU. To enable root guard, use the command: A switch does not enter any of these port states immediately except the blocking state. When the switch(config-if)# spanning-tree guard root Spanning Tree Protocol (STP) is enabled, every switch in the network starts in the blocking state and If the superior BPDUs are no more received, the port is restarts the normal STP states to return later changes to the listening and learning states. to normal use. 2. BPDU Guard - Here if any BPDU (superior or not) is received on a port configured with BPDU Blocking - During blocking state, the port is listening to and processing BPDUs After 20 seconds, guard, the port is immediately put into errdisable state. The port is effectively shutdown. the switch port changes from the blocking state to the listening state. To enable BPDU guard use the command at interface configuration mode: switch(config-if)# spanning-tree bpduguard enable Listening - After blocking, a root port or a designated port will move to a listening state. During the A port that is shutdown will continue to be in errdisable state even if the BPDUs are no longer listening state the port discards frames received from the attached network segment it also discards received.It is recommended to use bpdu guard on all ports that have portfast enabled. The frames switched from other ports for forwarding. At this state, the port receives BPDUs from the protection is useful for access layer nodes where the end user computers are expected to be network segment and directs them to the switch system module for processing. After 15 seconds, Connected. the switch port moves from the listening state to the learning state. 3. BPDU Skew Detection -It measures the amount of time that elapses from the expected time of arrival of a BDPU to the actual time of arrival of the BDPU. The arrival skew time condition is Learning - A port moves into the learning state after the listening state. During the learning state, reported via syslog messages. the port is listening for and processing BPDUs. In the listening state, the port starts to process user 4. Loop Guard - The loop guard is intended to provide additional protection against L2 forwarding frames and starts updating the MAC address table. Userframes are not forwarded to the destination. Loops (STP loops). For example, an STP loop is created when a blocking port in a redundant After 15 seconds, the switch port moves from learning to forwarding. topology erroneously transitions to forwarding state. The loop guard needs to be enabled on the non-designated ports to effectively prevent STP loops. Non-designated ports are the root port, Forwarding - Once in the forwarding state the port sends traffic. In a forwarding state, the port will alternate root ports,and ports that are normally blocking. The command used to enable loop process BPDUs, update its MAC Address table with frames that it receives, and forward user traffic guard is: Switch(config-if)# spanning-tree guard loop through the port Forwarding State is the normal operational state. The command is used at port level, loop guard is disabled by default on all switch ports. 5. Unidirectional Link Detection (UDLD) - The UDLD protocol allows devices connected through Disabled - A port in the disabled state does not participate in frame forwarding and is media such as fiber-optic or twisted-pair Ethernet to monitor the physical configuration of considered non-operational the cables and detect when a unidirectional link exists. If a unidirectional link is detected, UDLD shuts down the affected port and send out an alert. Spanning Tree Protocols a. Rapid Spanning Tree Protocol (RSTP) is based on the IEEE standard 802.1w. The standard has evolved from its predecessor 802.1D. 802.1w has the advantage of faster convergence over 802.1D.RSTP defines port states according to what the port does with the incoming frames. The allowed port states are as given below: 1. Discarding: The incoming frames are discarded. No MAC addresses are learned. 2. Learning: The incoming frames are dropped, but MAC addresses are learned. 3. Forwarding: The incoming frames are forwarded according to the learned MAC addresses. b. PVST (Per VLAN Spanning Tree) implementation has one instance of STP running for each VLAN. Therefore, whe there are 32 VLANs in the bridge network, there will be 32 instances of STP running. Also, each VLAN has a unique root, path cost etc. corresponding to that VLAN. Copyright © 2014 SimulationExams.com * All trademarks are duly recognized * Best printed in landscape mode CCNA Network Simulator CCNA Exam Simulator CCENT Exam Simulator CCNA ICND2 Exam Simulator CCNP BSCI Exam Simulator 19  Cisco™ CCNA : Router Redundancy Router Redundancy Protocols Important Features of HSRP 1. Hot Standby Router Protocol (HSRP): HSRP is a Cisco proprietary protocol that offers router redundancy. Here one router is elected as active router, and another router is elected as 1. HSRP authentication is carried out in clear text. standby router. All other routers are put in listen HSRP state. HSRP messages are exchanges using multicast destination address 244.0.0.2 to keep a router aware of all others in the group. 2. The hosts served by HSRP router use the IP address of virtual router as the default IP address. 2. Virtual Router Redundancy Protocol (VRRP): VRRP is very similar to HSRP. VRRP is a 3. When an Active router fails in HSRP environment, Standby router assumes the Active router role. standards based protocol and defined in RFC 2338. VRRP sends advertisements to multicast This new Active router will remain as Active router even if the failed Active router comeback to service, destination address 244.0.0.18 using IP protocol. irrespective of the priority levels. 3. Gateway Load Balancing Protocol (GLBP): GLBP overcomes some of the limitations of 4. The default HSRP standby priority is 100. If the standby priorities of routers participating in HSRP are HSRP/VRRP. Here, instead of just one active router, all routers in the group can participate same, the router with the highest IP address becomes the Active router. and offer load balancing. 5. Within the standby group of routers, the router with the highest standby priority in the group becomes 4. Server Load Balancing (SLB): SLB provides a virtual server IP address to which client the active router. For example, a router with a priority of 100 will become active router over a router with machines can connect. The virtual server, in turn, is a group of real physical servers arranged a priority of 50. The active router forwards packets sent to the virtual router. It maintains its active state in a server farm. by using Hello messages. 6. Each router in a standby group can be assigned a priority value. The range of priority values is between 0 and 255 (including 0 and 255). The default priority assigned to a router in a standby group is 100. The router with numerically higher priority value will become Active router in the HSRP standby group. 7. All routers in an HSRP standby group can send and/or receive HSRP message. Also, HSRP Members of HSRP Group protocol packets are addressed to all-router address (224.0.0.2) with a TTL of 1. Note that the HSRP messages are encapsulated in the data portion of UDP packets. 1. Virtual router: virtual router is what is seen by the end user device. The virtual router has its 8. In HSRP, the MAC address used by virtual router is made up of the following three components: own IP and MAC addresses. a. Vendor ID: The first three bytes of the MAC address correspond to the vendor ID. b. HSRP ID: The next two bytes of the MAC address correspond to HSRP code. It is always 07.ac. 2. Active router: Forwards packets sent to the virtual router.An active router assumes the IP