PE routers use IBGP to exchange VRF routes. As in all BGP configurations, this is accomplished by configuring BGP neighbors where the user wants to exchange routes. When the neighbors are configured in the same AS, it is an IBGP configuration. In addition, because MPLS LSPs are made between router loopback addresses, the [update-source loopback] parameters must be used. The following diagram shows two PE routers (PE 1 and PE 4) that are configured as BGP neighbors.
To configure IBGP on a Provider Edge router (PE) of a BGP or MPLS VPN network, the user must perform the configuration steps listed below.