MPLS VPN design - RR in forwarding path?

Nick Hilliard nick at
Wed Dec 31 13:09:40 UTC 2014

On 31/12/2014 12:08, Marcin Kurek wrote:
> I'm reading Randy's Zhang BGP Design and Implementation and I found
> following guidelines about designing RR-based MPLS VPN architecture:
> - Partition RRs
> - Move RRs out of the forwarding path
> - Use a high-end processor with maximum memory
> - Use peer groups
> - Tune RR routers for improved performance.
> Since the book is a bit outdated (2004) I'm curious if these rules still
> apply to modern SP networks.

arguably more so now than ever, but you can always run RRs inline in the
forwarding path if you want to.  Taking RRs out of the forwarding plane
means that you can keep your overall routing architecture simpler and more
consistent, and adding/removing different forwarding hardware means that
you don't really need to do much with the RR configuration.

The larger router vendors all have virtualised RR implementations these
days (XRv/CSR1k, vRR, AlcaLu, etc), which means that you can get to run
your RRs on standard x86 hardware platforms using normal hypervisors.  This
wasn't the case in 2004.  The pricing and licensing for virtual RR images
from the normal vendors hasn't settled down into workable models yet but
that's only a matter of time, particularly given that open source routing
stacks are going to start seriously impinging on this market segment in the
next couple of years.


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