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What type of routing protocols learn about other networks by sharing updates with neighbors?
What type of routing protocols learn about other networks by sharing updates with neighbors?
Which of the following is a key feature of link-state routing protocols?
Which of the following is a key feature of link-state routing protocols?
Which dynamic routing protocol is specifically designed for IPv6 networks?
Which dynamic routing protocol is specifically designed for IPv6 networks?
What is one disadvantage of using link-state routing protocols?
What is one disadvantage of using link-state routing protocols?
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Which of the following protocols uses distance vector routing?
Which of the following protocols uses distance vector routing?
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Which network does R3 send an update about out the Serial 0/0/1 interface?
Which network does R3 send an update about out the Serial 0/0/1 interface?
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What does R1 inform R3 about concerning network 10. 1. 0. 0?
What does R1 inform R3 about concerning network 10. 1. 0. 0?
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Which interface does R3 use to transmit updates for networks 10. 2. 0. 0 and 10. 3. 0. 0?
Which interface does R3 use to transmit updates for networks 10. 2. 0. 0 and 10. 3. 0. 0?
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What network update does R3 receive from R2?
What network update does R3 receive from R2?
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How does routing information remain after R1 and R3 exchange their updates?
How does routing information remain after R1 and R3 exchange their updates?
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What network update does R1 send out the Serial0/0/0 interface?
What network update does R1 send out the Serial0/0/0 interface?
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What network does R1 update out the FastEthernet0/0 interface?
What network does R1 update out the FastEthernet0/0 interface?
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From which router does R1 receive an update, and what metric is associated with that update?
From which router does R1 receive an update, and what metric is associated with that update?
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What happens to the network 10.3.0.0 in R1's routing table?
What happens to the network 10.3.0.0 in R1's routing table?
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Which interface does R1 use to send an update about the network 10.3.0.0?
Which interface does R1 use to send an update about the network 10.3.0.0?
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Which of the following routing protocols is considered classful?
Which of the following routing protocols is considered classful?
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What is a key characteristic of link-state routing protocols?
What is a key characteristic of link-state routing protocols?
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Which of the following protocols supports variable length subnet masks (VLSMs)?
Which of the following protocols supports variable length subnet masks (VLSMs)?
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What is the primary purpose of a routing protocol's metric?
What is the primary purpose of a routing protocol's metric?
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Which of the following protocols is specifically designed for classless routing?
Which of the following protocols is specifically designed for classless routing?
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When a router detects a topology change, it cannot advertise this change to other routers.
When a router detects a topology change, it cannot advertise this change to other routers.
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R1 learns about the 10.2.0.0 network via its Serial 0/0/0 interface.
R1 learns about the 10.2.0.0 network via its Serial 0/0/0 interface.
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R3 adds the 10.4.0.0 network available through its FastEthernet 0/0 interface.
R3 adds the 10.4.0.0 network available through its FastEthernet 0/0 interface.
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R2 communicates the 10.3.0.0 network through its Serial 0/0/1 interface.
R2 communicates the 10.3.0.0 network through its Serial 0/0/1 interface.
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The network 10.1.0.0 is added to R1's routing table.
The network 10.1.0.0 is added to R1's routing table.
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R1 stores network 10.4.0.0 in the routing table with a metric of 2.
R1 stores network 10.4.0.0 in the routing table with a metric of 2.
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R2 sends updates about networks 10.1.0.0 only out of Serial 0/0/0 interface.
R2 sends updates about networks 10.1.0.0 only out of Serial 0/0/0 interface.
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The metric for network 10.3.0.0 received by R1 from R2 is 1.
The metric for network 10.3.0.0 received by R1 from R2 is 1.
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R1 does not change its routing information for network 10.3.0.0 after receiving an update from R2.
R1 does not change its routing information for network 10.3.0.0 after receiving an update from R2.
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The FastEthernet0/0 interface on R1 does not receive any updates.
The FastEthernet0/0 interface on R1 does not receive any updates.
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RIPv1 is a classful routing protocol that sends subnet mask information in its updates.
RIPv1 is a classful routing protocol that sends subnet mask information in its updates.
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OSPF is a link-state routing protocol and is standards based.
OSPF is a link-state routing protocol and is standards based.
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Classless routing protocols support variable length subnet masks (VLSMs).
Classless routing protocols support variable length subnet masks (VLSMs).
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Only RIPv2 and EIGRP are considered classless routing protocols.
Only RIPv2 and EIGRP are considered classless routing protocols.
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Routing protocols determine the best path based on the route with the highest cost.
Routing protocols determine the best path based on the route with the highest cost.
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Interior Gateway Protocols (IGP) are used for routing within an AS.
Interior Gateway Protocols (IGP) are used for routing within an AS.
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RIP and EIGRP are examples of Exterior Gateway Protocols (EGP).
RIP and EIGRP are examples of Exterior Gateway Protocols (EGP).
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Exterior Gateway Protocols (EGP) are used for routing between Autonomous Systems.
Exterior Gateway Protocols (EGP) are used for routing between Autonomous Systems.
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OSPF is a type of Exterior Gateway Protocol (EGP).
OSPF is a type of Exterior Gateway Protocol (EGP).
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The official routing protocol used by the Internet is classified as an Interior Gateway Protocol (IGP).
The official routing protocol used by the Internet is classified as an Interior Gateway Protocol (IGP).
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Study Notes
Chapter 8: Routing Dynamically
- Cisco Networking Academy is a program
- This chapter covers dynamic routing protocols
- Dynamic routing protocols are used in networks since the late 1980s
- Newer versions support communication based on IPv6
Routing Protocols Classification
- Interior Gateway Protocols (IGPs):
- Distance Vector: RIPv2, IGRP, EIGRP
- Link-State: OSPF, IS-IS
- Exterior Gateway Protocols (EGPs):
- Path-Vector: BGP
Chapter 8: Objectives
- Explain the basic operation of dynamic routing protocols
- Compare and contrast dynamic and static routing
- Determine which networks are available during an initial network discovery phase
- Define different categories of routing protocols
- Describe how distance vector routing protocols learn about other networks
- Identify types of distance vector routing protocols
- Configure the RIP routing protocol
- Explain how link-state routing protocols learn about other networks
- Describe information sent in a link-state update
- Describe advantages and disadvantages of using link-state routing protocols
- Identify protocols that use link-state routing (OSPF, IS-IS)
- Determine route source, administrative distance, and metric for a given route
- Explain the concept of a parent/child relationship in a dynamically built routing table
- Compare IPv4 classless route lookup process
- Analyze a routing table to determine which route will be used to forward a packet
Dynamic Routing Protocol Operation
-
Purpose: facilitating routing information exchange between routers
- Discover remote networks
- Maintain up-to-date routing information
- Choose the best path to destination networks
- Find a new best path if the current one is unavailable
-
Main components:
- Data structures: tables or databases in RAM to store routing information.
- Routing protocol messages: used to discover neighbors, exchange routing info, and learn about the network
- Algorithm: used to facilitate routing information and determine the best path
Dynamic Routing Protocol Operation (cont.)
- EIGRP creates and maintains tables:
- Neighbor table
- Topology table
- EIGRP uses the DUAL algorithm to determine the best routes
- Routing protocols create and maintain data structures
- Routing protocols exchange messages
- EIGRP Hello
- EIGRP Update
- EIGRP Query
- EIGRP Reply
- EIGRP Acknowledge
Dynamic Routing Advantages and Disadvantages
- Advantages:
- Suitable for all topologies with multiple routers
- Generally independent of network size
- Automatically adapts to topology changes to reroute traffic
- Disadvantages:
- Can be complex to implement
- Less secure
- Route depends on current topology
- Requires additional CPU, RAM, and link bandwidth
Static Routing Advantages and Disadvantages
- Advantages:
- Easy to implement in small networks
- Very secure
- Route to destination is always the same
- No routing algorithm or update mechanism required
- Disadvantages:
- Suitable only for simple topologies
- Manual intervention is needed to re-route traffic
Routing Protocol Operating Fundamentals
- Dynamic Routing Protocol Operation
- Router sends and receives routing messages on its interfaces
- Router shares routing messages and info with other routers that use the same protocol
- Routers exchange routing information to learn about remote networks
- When a router detects a topology change, the routing protocol advertises this change to other routers
- Cold Start: direct network detection by routers
Routing Protocol Operating Fundamentals (cont.)
-
Network Discovery: initial exchange
- R1, R2, and R3 send updates about their networks
- Routers store and update routing tables with new acquired information
-
Next Update: update exchange between routers
-
Network discovery initial exchange (cont.)
- R2 updates networks 10.3.0.0 and 10.4.0.0 to remaining routers
- R3 updates networks 10.1.0.0 to remaining routers
-
Exchanging Routing Information
-
R1, R2, R3 send updates
-
Updates can contain information about network and metrics
-
No changes mean that the information remains the same
Routing Protocol Operating Fundamentals (cont.)
- Achieving Convergence
- Network converges when all routers have complete and accurate info about the network
- Convergence takes time to share info, calculate best paths, and update routing tables
- Network topology must converge to become operable
- Propagation speed for routers to forward routing information can affect convergence speed
- Older protocols (RIP) converge more slowly than modern protocols (EIGRP, OSPF)
- Network Discovery
- Routers initially discover directly-connected networks
- Routers exchange routing updates to learn about remote networks
Types of Routing Protocols
-
Classifying routing protocols
-
Interior Gateway Protocols (IGPs): Distance vector, Link-state
-
Exterior Gateway Protocols (EGPs): Path-vector
-
Distance vector protocols use routers as sign posts along the path to the final destination network.
-
Link-state protocols are like having a complete map of the network topology, avoiding the need for sign posts
Types of Routing Protocols (cont.)
- Classful routing protocols do not send subnet masks in their routing updates
- Only RIPv1 and IGRP are classful and don't include subnet mask info in updates.
- Classless routing protocols include subnet masks in routing updates
- RIPv2, EIGRP, OSPF, IS-IS use subnet masks in routing updates and support VLSM, CIDR features of IPv6 protocols.
Routing Protocol Characteristics
- A table comparing various routing protocols (RIPv1, RIPv2, IGRP, EIGRP, OSPF, and IS-IS) using various characteristics.
- Speed of convergence
- Scalability
- Network size
- VLSM support
- Resource usage
- Implementation complexity
Routing Protocol Metrics
- Metric: a measurable value assigned by the routing protocol
- Used to determine the overall cost of a path from source to destination
- Routing protocols use the route with the lowest cost as the best path
Distance Vector Routing Protocol Operation
- Distance vector routing protocols: share updates, are not aware of network topology
- Some protocols send periodic updates even when topology hasn't changed
- Updates consume bandwidth and network device CPU resources
- RIPv2 and EIGRP use multicast addresses
- EIGRP only sends updates when topology changes
Distance Vector Routing Protocol Operation (cont.)
- Purpose of routing algorithms: send and receive routing updates, calculate best paths, react to topology changes
- RIP uses Bellman-Ford algorithm
- IGRP and EIGRP use Diffusing Update Algorithm (DUAL)
Types of Distance Vector Routing Protocols (cont.)
- RIPv1 vs RIPv2:
- RIPv1 sends updates every 30 seconds using UDP port 520; RIPv2 updates use a different UDP port, supports VLSM and CIDR features
- RIPng is based on RIPv2, with a hop limitation and administrative distance of 120
Enhanced Interior-Gateway Routing Protocol
- IGRP vs EIGRP
- Metric: composite metric(s) including bandwidth, delay, reliability, load for better path selection
- EIGRP is more efficient, provides better convergence than IGRP due to periodic updates being triggered only on changes and better performance
Configuring the RIP Protocol
- Configuring RIP networks: use commands like
router rip
,network
, andpassive-interface
- Verifying RIP settings
- Configuring passive interfaces on routers
- Sending updates over a LAN impacts the network in several different ways which can be categorized as three types: wasted bandwidth, wasted resources, security risk
- Enable RIPv2
- Disable auto summarization on a RIP v2 router
Configuring the RIP Protocol (cont.)
- Propagate a default route
- Configure a default route on a router and verify it is advertised using
ip route
anddefault-information originate
commands
Link-State Routing Protocol Operation
- Dijkstra's algorithm: calculate the shortest path in a graph, determining the optimal route from the source to the destination nodes
- Link-state updates
- Each router learns about directly connected network
- Each routers is responsible for 'saying hello' to its neighbors on directly connected networks
- Each router creates link state packets (LSP) about direct links
- Router floods LSP to all neighbors
- Link-state database building: each router uses the collected LSPs and SPF algorithm to build a map of topology
- OSPF protocol; IS-IS Protocol
- Building the SPF tree
- Populate the routing table for collected remote networks
Link-State Updates (cont.)
- Building the SPF Tree
- Identify directly connected networks
- Each router identifies its directly connected neighbors
- Using this information, each router computes the shortest path to all remote networks
Link-State Updates (cont.)
- Adding OSPF routes to routing tables
- Adding destination networks
- Show ip protocols command to verify the configuration settings for IPv4 routing protocols or show ipv6 protocols for IPv6
Why Use Link-State Protocols
- Advantages:
- Each router builds its own topological map to determine the shortest path
- Immediate flooding of LSPs achieves faster convergence
- LSPs are sent only when there's a change and contain relevant info
- Hierarchical design facilitates implementation of multiple areas
- Disadvantages:
- Requires additional memory for link-state database and SPF tree
- Calculating the SPF algorithm requires additional CPU processing
- Bandwidth can be affected by link-state packet flooding
Protocols that Use Link-State
- Open Shortest Path First (OSPF)
- OSPFv2 (IPv4)
- OSPFv3 (IPv6)
- Intermediate System to Intermediate System (IS-IS)
Parts of an IPv4 Route Entry
- Route table entries
- Directly connected interfaces: show ip route command used to show directly connected interfaces
- Remote networks entries: show ip route command used to show remote networks
Chapter 8: Summary
- Dynamic routing protocols used by routers to automatically learn about remote networks from other routers
- Purpose: discovery, up-to-date info, choosing best paths to destinations, finding new paths if current ones unavailable
- Best for large networks but static routing better for stub networks
- Categorized as classful or classless, distance vector or link-state, and interior or exterior gateway protocols
- Link-state protocols use Dijkstra's algorithm to calculate the best path
- Cisco routers use administrative distance to choose which sources to use
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Test your understanding of dynamic routing protocols, including link-state and distance vector protocols. This quiz covers key concepts, advantages, and disadvantages of various routing mechanisms. Perfect for networking students and professionals.