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

Ian Dickinson iand at eng.pipex.net
Tue Feb 7 03:43:38 EST 2006

You're matching and accepting the default route, but the implicit
deny on the end of the route-map is killing the customer routes.
Simple fix is to add the following and you'll be sorted.

route-map he-def-prepend permit 100

There are many other approaches to this too.


Charles Sporkman wrote:
> Hello,
> 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
> permanently)...
> 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
> routes...
> Thanks,
> Charles
Ian Dickinson
Development Engineer
ian.dickinson at pipex.net

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