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Understanding Router Communication and Routing Protocols in Networking

This document explores how routers, such as Router X and Router Y, acquire knowledge about different networks (A, B, C) through static routes and routing protocols. It highlights the effectiveness of static routing in simple networks while noting the configuration challenges in larger setups. We delve into the functionalities of routing protocols like RIP (Routing Information Protocol), focusing on their ability to share reachability information, determine optimal paths, and react to network changes. Key algorithms and methods, such as Split Horizon and Poison Reverse, are discussed to illustrate routing concepts.

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Understanding Router Communication and Routing Protocols in Networking

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Presentation Transcript

  1. How does Router Y know about Network A? How does Router X know about Network C?

  2. One Solution • Static Routes • Effective in simple networks without alternate paths • Still difficult to configure if you have, for example, 20 routers and 100 networks in a tree structure.

  3. ROUTER X: ip route 192.168.3.0 255.255.255.0 192.168.2.2 ROUTER Y: ip route 192.168.1.0 255.255.255.0 192.168.2.1

  4. What is the best path from Net 1 to Net 3? If a Link goes down, can an alternate path be determined correctly and quickly?

  5. Routing Protocols • Communication between routers to share information about the reachability and status of networks. • The ultimate goal is to allow hosts to communicate with other hosts. • Most hosts will not participate in these routing protocols. The internetwork is an abstract service, much like a file system.

  6. Routing Protocol Basics A routing algorithm must: • Pass reachability info to other routers • Receive reachability info from other routers • Determine optimal routes • React to changes

  7. RIP • Routing Information Protocol • Popularity due to distribution of Berkeley UNIX (1982) and routing daemon: routed • Distance Vector ( Bellman-Ford) routing protocol • RIP v1 is classful, RIP v2 is classless.

  8. RIP Algorithm Basics • Advertise my directly connected networks, with a metric (hop count) of 1, via broadcast on my directly connected networks,. • Listen. If I hear other RIP advertisements, add to my route table if the network is new to me, or if the metric is better. • Re-advertise periodically, including nets that I heard about. (Add 1 to these metrics).

  9. More RIP details • Split Horizon - Don’t announce routes I learned back out the same interface. • Poison Reverse – Announce routes back out the same interface, but with metric 16 (unreachable). • Ethereal sniffer

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