Hello Paul,
We have the capability to bring up iBGP on the 6500's which we might examine
(just never needed to). I think it's safe to assume in our environment that
if we brought up full tables on the 6500's using iBGP that there is no need
to redistribute anything into OSPF as they will become aware of the route
anyways.
we still have a few very old boxes with little memory and
some funky leased lines connected to that
also participate in iBGP to learn some customer routes
(<100). Works like a charm. I would strongly vote to this
way but if you do not ...
If we didn't do that, would it be best to redistribute on the 7600's (EBGP
to OSPF) or would it be better at the 3825 side of things (which we manage
and have full control over - it participates in OSPF as well)? I'm thinking
it would make more sense at the 3825 side?
I'd build the tree from the center (7600s) and set up
redistribution (or iBGP stuff) from there. Let the relevant
access routers get to know about the routes from where the
routes are originally learned through eBGP.
But thats just my way of doing it.
Good luck!
Sascha
-----Original Message-----
From: Sascha E. Pollok [mailto:nsp-l...@pollok.net]
Sent: Tuesday, April 06, 2010 11:03 AM
To: Paul Stewart
Cc: cisco-nsp@puck.nether.net
Subject: Re: [c-nsp] BGP - Multihop across igp network
Hello Paul,
Connected to these 7600's we have a pair of 6500's not doing BGP (however
participating in OSPF as all our boxes do)
Connected off one of the 6500's we have a 3825 at a customer site
The customer who is connected to a 3825 wants a full BGP feed from us.
So, I created a pair of ebgp-multihop sessions between the 3825 and our
two
7600's - both tables populated and everything looked good. Once the
customer brought up their session all the traffic seems to loop between
our
networks.. Almost like a blackhole effect. In our 7600's I can see the
customer routes advertising out and BGP itself looks correct when I do a
"show ip bgp xxxxx" towards one of their netblocks.
Your other routers need to know about the customer's network.
You can either redistribute the customer's EBGP prefixes
into OSPF (selectively using e.g. route-maps on the 7600's)
or talk BGP to your other routes but learn only the customer's
routes. We are doing a similar thing. We are tagging customer-learned
routes with a BGP community and announce only prefixes carrying
this community via IBGP to the access routes.
Thus, the access routers carry only a few prefixes and can perfectly
route towards the customer.
Sascha
--
Sascha E. Pollok E-Mail: s...@iphh.net
Leiter Netzwerkdesign und -betrieb Tel: +49 (0)40 374919-10
IPHH Internet Port Hamburg GmbH Fax: +49 (0)40 374919-29
Wendenstrasse 408 AG Hamburg, HRB 76071
D-20537 Hamburg Geschaeftsfuehrung: Axel G. Kroeger
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