BGP Redistribute-internal and MPLS

vdadlaney · ‎06-02-2008

Hi, usually when redistributing from BGP into IGP only EBGP routes are redistributed unless the bgp redistribute-internal command is configured which allows the redistribution of IBGP routes. However when doing the same redistribution on a PE router for a IGP running with the CE it seems that this command is not needed and IBGP routes still get redistributed into the IGP. It works without this command. Does anyone know why this is the case?

I have been trying to understand this for some time now and it seems very trivial however its been bugging me and was hoping someone could clarify. Thx

mohammedmahmoud · ‎06-02-2008

Hi Vikram,

Well, look at it this way, in the case of MPLS VPN, BGP between the PEs (address-family ipv4 vrf x) is used to transport the customer routes between CEs, and thus it is very logical that it should redistribute all kind of routes (in the case of MPLS VPN the customer routes are always going to be iBGP anyway since they are redistributed from IGP (PE-CE) on another PE - except on the local router when the customer is using BGP as the PE-CE routing protocol) - using another prospective, redistributing iBGP routes into IGPs may cause routing loops to form within an autonomous system, but in the case of PE-CE the redistribution is done into a routing protocol outside the BGP domain (customer side).

I hope that i've been informative.

BR,

Mohammed Mahmoud.