[c-nsp] prefix-list/route-map quandry

Chris Hale chris-lists at pipelinewireless.us
Mon Feb 6 23:19:01 EST 2006

Can you show us the output of the following commands:

Show ip bgp summary
Show ip bgp neighbor received-routes
Show ip route

If you want to prefer the incoming routes from ISP X over ISP Y, I would
just use the local-preference or weight options as previously recommended.
It seems as though the reason you are receiving the BGP routes but not
putting them into the routing tables is a routing issue to the next hop.

router#sh ip bgp
BGP routing table entry for, version 1868955
Paths: (1 available, no best path)
  Not advertised to any peer
  6939, (received-only) <<---
******************** from ( <------ Do you have a
route to either of these IPs?
      Origin IGP, metric 1, localpref 100, valid, external

-----Original Message-----
From: Charles Sporkman [mailto:spork.sporkman at gmail.com] 
Sent: Monday, February 06, 2006 9:32 PM
To: cisco-nsp at puck.nether.net
Subject: [c-nsp] prefix-list/route-map quandry


I'm getting a little bit stuck here.  I spent the better part of
friday evening looking at the "IOS Essentials for ISPs" book and at
the resulting config and just walked away scratching my head...

What I want to do seems pretty simple (I think).  I have two
upstreams.  No problems with announcing my prefixes, everything's
fine.  Inbound, they are both giving me default, and one "ISP X" is
giving me customer routes as well.  "ISP Y" is my preferred provider. 
I want to use "ISP X" for:

-backup if I lose "ISP Y"
-I want to send any traffic destined to their customers to them directly

So in essence, I want to pad the incoming default route from them, but
not the customer routes.  I'm doing the following right now, and not
seeing any customer routes in the table (but they are being received
according to "sh ip bgp x.x.x.x"):

 neighbor remote-as 6939
 neighbor description Hurricane Electric
 neighbor password <removed>
 neighbor update-source Loopback0
 neighbor version 4
 neighbor soft-reconfiguration inbound
 neighbor prefix-list bgp-out out
 neighbor route-map he-def-prepend in
 neighbor route-map prepend-us out
ip prefix-list he-match-def permit
route-map he-def-prepend permit 1
 description prepend on default route only
 match ip address prefix-list he-match-def
 set as-path prepend 6939

I'm totally new to prefix-lists, somewhat rusty with route maps, and
pretty much lost on using them together.  What's gone awry here?  The
rule is working as far as prepending an extra hop on the received
default, but the other routes are not showing up anywhere.  As you can
see, I currently have no inbound filters (yes, I don't want to do that

Just so we can all see that I am hearing their routes:

router#sh ip route
% Network not in table
router#sh ip bgp
BGP routing table entry for, version 1868955
Paths: (1 available, no best path)
  Not advertised to any peer
  6939, (received-only) <<--- from (
      Origin IGP, metric 1, localpref 100, valid, external

I'm probably doing something really stupid and blaming it on the route
map.  Just not sure what I'm doing that would stop the received



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