Abstract
- Distance Vector: ‘routing via rumor’ in which each router shares info about the routes they know and cost. Routers don’t have the entire view of the network
- Link State: every router creates a ‘connectivity map’ of the network. Every route will advertise info about its connected network to its neighbours. Each router will have the same map and use the same map to calculate the best routes to each destination. This requires more resources and faster to react to changes (usually a few seconds)
IGP vs EGP
IGPs (OSPF, EIGRP, etc.) use metrics like cost, bandwidth, or hop count to figure out the best route within an AS.
Border Gateway Protocol (the main EGP) doesn’t replace IGP. Instead, iBGP relies on the IGP to actually move packets between iBGP peers, while iBGP’s job is to share Internet routes (learned via eBGP) across the AS.