What is the difference between eBGP and iBGP routing protocols in BGP?

What is the difference between eBGP and iBGP routing protocols in BGP?

Border Gateway Protocol (BGP) uses two main types of routing protocols: external BGP (eBGP) and internal BGP (iBGP). The main difference between eBGP and iBGP lies in how they handle routing information and the relationships they have with other BGP peers.

eBGP (External BGP)

• eBGP is used to exchange routing information between different autonomous systems (AS).
• eBGP typically runs between routers in different AS, and the distance between them is considered to be external to the AS.
• eBGP peers must be directly connected, or a loopback interface is used with a static route to establish the BGP peering.
• eBGP uses a different Autonomous System Path (AS Path) to prevent loops in routing updates between different AS.

iBGP (Internal BGP)

• iBGP is used to exchange routing information within the same autonomous system (AS).
• iBGP typically runs between routers in the same AS, and the distance between them is considered internal to the AS.
• iBGP peers do not need to be directly connected but must have a full mesh of BGP connections within the AS, or route reflectors and confederations can be used to reduce the number of peering sessions.
• iBGP carries the full BGP routing table which is necessary for internal routing within the AS.

Overall, the key distinction between eBGP and iBGP is that eBGP is used for exchanging routing information between different AS, while iBGP is used for disseminating routing information within the same AS.