Day 9 & 10 : Intro to Routing Protocols

Static routes are not scalable in large networks. Routing protocols automatically adveertised routing information throughout the network. Routers dynamically learn new routes and remove failed routes.

There are 2 categories of routing protocols based on their use.
1. Interior Gateway Protocols (used in a single organization/autonomous system)
(a) RIP (Routing Information Protocol)
(b) IGRP (Interior Gateway Routing Protocol)
(c) EIGRP (Enhanced IGRP)
(d) OSPF (Open Shortest Path First)
(e) IS-IS (Intermtediate system to Intermediate System)

2. Exterior Gateway Protocols (used for Inter autonomous system/the Internet)
(a) BGP (Border Gateway Protocol)

Routing protocols are also categorized based on their computational algorithm.
1. Distance Vector Protocol
(a) RIP
(b) RIP version 2
(c) IGRP
2. Link State Protocol
(a) OSPF
(b) IS-IS
3. Hyprid (mix of DV and LS)
(a) EIGRP
4. Path Vector
(a) BGP

- Algorithm used in EIGRP is called DUAL (Diffused Update Algorithm)
- IGRP and EIGRP are Cisco proprietary algorithm
- Algorithm used in OSPF and IS-IS is called Dijkstra's Shortest Path First (SPF) algorithm

- DV routing protocols (except RIPv2) do not send subnet mask information in routing updates. Those protocols use default subnet mask based on class of IP address. For that reason, DV routing protocols are called Classful routing protocols.
Classful routing protocols do not support VLSM (variable length subnet mask)

- All routing protocols, except RIP and IGRP, send subnet mask information in routing updates. These routing protocols are known as Classless routing protocols.
Classless routing protocols support VLSM.