Boarder gateway protocol (BGP)
This is a class of protocols that are used for interdomain routing. That is sharing subnets between AS. Two routers connected over BGP are called BGP peers. They open a semi-permanent TCP connection where they exchange routes. There are two varieties of this class.
- iBGP: For internal to the AS communication between boarder routers.
- eBGP: For two routers who are in different AS. The difference between iBGP and IGP is that iBGP is communicating about what external subnets are available from that router wheres IGP is communicating about what internal subnets there are.