Regarding IGP and BGP

[ncnaveen_arasu]

Hi team

Why we run IGP (OSPF) and BGP in MPLS VPN envirornment. wether runing BGP is not sufficient, why we need IGP also. PLease clarify in brief

[Raju Sekharan · Accepted solution]

Hi Naveen,

Are you talking about OSPF as PE-CE protocol or OSPF used in the MPLS service provider network

[ncnaveen_arasu]

Hi Rajs,

Thanks for the reply, iam talking about the OSPF used in the MPLS service provider network. When we run BGP between the loopbacks between PE and P router. why we run again an OSPF or some IGP protocol.

[cadet alain]

Hi,

you do your PE-PE BGP peering over Loopbacks and so you need an IGP for the peering and also  a MPLS router will advertise labels only for prefixes it has in its routing table( so in CEF table).

Regards.

Alain

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[sivai2tech]

Naveen,

Here is why we need IGP in the core.

                             igp

CE1---------PE1----------P----------PE2----------CE2

                            mpls

1.> To establish MPBGP session b/w PEs.

2.> To establish LSP.(signalling is based on the igp that you use in the core).

Thx!

~S