MPLS VPN design - RR in forwarding path?

Mark Tinka mark.tinka at
Thu Jan 8 15:09:03 UTC 2015

On Friday, January 02, 2015 11:03:21 PM Daniel Rohan wrote:

> Also think physical topologies like ethernet rings. 
> Where's the RR go in this topology?

In these topologies, I've been playing with having the RR's 
in the core (i.e., on the other end of the PE Aggregation 
routers terminating the ring) and running the iBGP sessions 
between the Metro-E Access switches and the RR's.

As the RR's are MPLS-free (but the Metro-E Access switches 
[particularly Cisco] still assign MPLS labels to each IGP 
route), we cobble together a combination of hop-by-hop IP 
forwarding + MPLS forwarding fu to get traffic to where it 
needs to go without involving the PE Aggregation routers in 
the routing toward the Metro-E Access switches (i.e., 0/0 
and ::/0 + a few more specifics come from the RR's).

Been working with this routing topology for MPLS rings since 
2009. It seems to hold up...

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