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

[Charles Sporkman]

On 2/7/06, Ian Dickinson <iand at eng.pipex.net> wrote:

> There are many other approaches to this too.

Are there ever...  This was a pretty fun little learning experience. 
RIght now I went with just a simple route-map that prepends
Hurricane's AS one time to everything (the n00b method).  That works -
default is L3, backup is Hurricane, and I send traffic for their nets
to them.

However over the next few weeks I'm going to try all the other
approaches late at night just so I'm clear on how they work.  The
route-map/prefix-list interaction confuses me the most, so I'll try
that next.

Thanks for all your help, it's appreciated.

Charles

> Ian
>
> 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 10.1.1.2 remote-as 6939
> >  neighbor 10.1.1.2 description Hurricane Electric
> >  neighbor 10.1.1.2 password <removed>
> >  neighbor 10.1.1.2 update-source Loopback0
> >  neighbor 10.1.1.2 version 4
> >  neighbor 10.1.1.2 soft-reconfiguration inbound
> >  neighbor 10.1.1.2 prefix-list bgp-out out
> >  neighbor 10.1.1.2 route-map he-def-prepend in
> >  neighbor 10.1.1.2 route-map prepend-us out
> > !
> > ip prefix-list he-match-def permit 0.0.0.0/0
> > !
> > 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 216.218.186.0
> > % Network not in table
> > router#sh ip bgp 216.218.186.0
> > BGP routing table entry for 216.218.128.0/17, version 1868955
> > Paths: (1 available, no best path)
> >   Not advertised to any peer
> >   6939, (received-only) <<---
> >     209.51.171.25 from 209.51.171.25 (216.66.23.98)
> >       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
> PIPEX
> ian.dickinson at pipex.net
> http://www.pipex.net
>
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