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Routing & Switching · Intermediate

Internal BGP (iBGP)

A BGP session between routers in the same autonomous system.

Definition

iBGP carries external routes across an AS without changing AS_PATH or, by default, the next hop. An iBGP-learned route is not advertised to other iBGP peers (iBGP split horizon), so a full mesh, route reflectors or confederations are required. Sessions are typically sourced from loopbacks.

Example

neighbor 10.255.0.2 remote-as 65001 / neighbor 10.255.0.2 update-source Loopback0

Exam tip

Missing next-hop-self on edge routers makes eBGP next hops unreachable to iBGP peers, a classic fault.

Don't confuse it with

Related terms