[c-nsp] Routing Question

[Gert Doering]

Hi,

On Thu, Jun 02, 2011 at 10:28:27PM -0400, Joseph Hardeman wrote:
> Thanks for the reply, I was hoping there was some way to do it with
> Local-Prefs or weights setting the BGP routes from peers into a group and
> then selecting that group from the routing table for the internal IP Range I
> want to use those routes.  

There is only one routing table.  And no way to select different bits of
it according to source address (unless you use policy routing, but that
won't easily do what you want either).

> I presume there is a way to setup VRFs to do this?  

Yes.  As Tony already explained, VRFs are to a router what VLANs are to
a switch - the router is divided into multiple virtual routers, and all
of them have their own routing table.

So you put one set of source machines into VRF blue and the other into
VRF red, and then you can pref the routes individually to whatever you
want.  Getting the routes into the VRFs depends on your router setup,
and can be its own challenge.

> Or how would that work?  I believe VRFs are specific for an MPLS
> network and I have never touched or set one of those up before.

MPLS is just one possible option to transport VRF-belonging packets to
other routers (like "dot1q tagging for VLAN-packets", in a way).  But 
the VRF functionality is independent of MPLS, and you could, for example,
connect multiple VRF-enabled routers via a dot1q trunk, with every VLAN
interconnecting one of the VRFs.  (This gets impractical after a few
VRF instances, and MPLS/LDP/BGP-AFI-VPNv* makes this all automatic).

gert
-- 
USENET is *not* the non-clickable part of WWW!
                                                           //www.muc.de/~gert/
Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de
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