- Dynamic routing is when protocols are used to find networks and update routing tables on routers
- Two types of routing protocols are used in internetwork: interior gateway protocols (IGPs) and exterior gateway protocols (EGPs)
- IGPs are used to exchange routing info with routers in the same autonomous system (AS)
- An AS is a collection of networks under the same administrative domain (all routers sharing the same routing table info)
- EGPs are used to communicate between ASes. ( ie. Border Gateway Protocol - BGP)
- Administrative distance (AD) is used to rate the trustworthiness of routing info received on a router from a neighbour router
- AD is an integer from 0 - 255 with 0 is the most trusted and 255 means no traffic will be passed via this route
- AD, routing protocol metrics ( hop count, bandwidth) are used to determine best path to remote network:
- There are three classes of routing protocols: Distance vector, Link state & Hybrid
- Distance-vector protocols find the best path to a remote network by judging distance - #s of hop. (ex. RIP, IGRP)
- Link-state protocols (Shortest-path-first protocol) create three separate tables: one keeps track of directly attached neighbors, one determines the topology of entire internetwork, one used as routing table. (ex. OSPF)
- Hybrid protocols used both distance-vector and link-state protocols. (ex. EIGRP)
