The MPLS-OPS Archive

[Nathan <paranoia@phreaker.net>]

Hi,

I've got an annoying problem. I have a vrf that uses OSPF
internally. To begin with, 2 PE routers conversing using 
classical MP-BGP. Then as I added links, I got a problem: 
packets coming in to a PE preferred to go out towards a CE
linked to that same PE, even when it was much more efficient 
to use the other PE router to access a different CE. I traced
that to the fact that IBGP links get a higher administrative
distance, 200 instead of 110 for OSPF, so even if the OSPF cost 
on the connected CE link is 10000 and the OSPF cost on the
CE link connected to the other PE is 10, the administrative
distance wins out (the OSPF cost between the PEs is as far a
I can see not taken into account at all, not that I care much 
about it).

I looked at modifying the administrative distance, but that's
system-wide, which would break loads of things.

What I did was to set up a VLAN on other interfaces of the two
PEs, then ran OSPF over that, no problem.

Now I have to add links on a PE that does not have a convenient
second interface for VLANs, just a single tag-switching
interface and a lot of CE links.

"OSPF Support for Forwarding Adjacencies over MPLS Traffic 
Engineered Tunnels" looks promising, but the document doesn't 
mention "vrf" once, and apparently it only exists on S/SXE/SBC
trains (I'm running 12.2T and I don't even know what the S
trains correspond to, do you need a different license? I know I
use lots of features of 12.2T that aren't in 12.2 mainstream).

I just want to pass the OSPF metric unaltered from one PE to the
other . . . (unaltered or with the PE-PE cost added in, I don't
really care).

What should I do?

Thanks for any help!

Nathan

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