Dynamic Routing Protocols Quiz

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, and passive-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 and default-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

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.