[nsp] Regular expressions as-path filter lists

[Ahmer Ghazi]

At the egress router, your AS number will be prepended before the advertisement is being sent to your upstream.  You should include that in your as-path access-list applied outbound towards your ISP; e.g. ip as-path access-list 2 permit ^789_456


Ahmer Ghazi

-----Original Message-----
From: Jim Devane [mailto:jim at powerpulse.cc] 
Sent: Thursday, April 24, 2003 1:58 PM
To: cisco-nsp at puck.nether.net
Subject: [nsp] Regular expressions as-path filter lists

Hello all,

Regular expressions are kicking my butt.

I am having trouble letting an advertisement from a customer downstream traverse my router. I cannot seem to get the advertisement to pass through to my upstream provider.

Specifically, they are multi-homed and have 3 networks. They wish to prepend the other ISP's address space to us and our address space prepended to the other ISP. Fair enough. 

I am getting the prepends in my routing table but I CANNOT get them to pass through to my upstream. I AM able to get them to an iBGP peer if I permit all advertisements.

There are no ACLs or prefix list...only as-path lists...below is what I have.

Here's what I have:

nei 1.1.1.1 remote-as 123 ( my upstream)
nei 1.1.1.1 filter-list 1 in
nei 1.1.1.1 filter-list 2 out
nei 2.2.2.2 remote-as 456 ( my customer)
nei 2.2.2.2 filter-list 3 in
nei 2.2.2.2 filter-list 1 out

ip as-path access-list 1 permit .*

ip as-path access-list 2 permit ^$
ip as-path access-list 2 permit ^789$ (my AS)
ip as-path access-list 2 permit ^456

ip as-path access-list 3 permit ^456

So, when I do a show ip bgp regexp ^456 I get something like:

BGP table version is 10, local router ID is 3.3.3.3

   Network          Next Hop            Metric LocPrf Weight Path
*  169.254.1.0/22   2.2.2.2                          0     456 456 456 456  i
*  192.168.47.0/22   2.2.2.2                          0     456 i
*  172.29.29..0/24   2.2.2.2            0             0     456 456 456 456 i


When I look to see what is advertised to my upstream:

sh ip bgp nei 1.1.1.1 adv

None of those three routes show up. They DO show up if I look for them (sh ip bgp 169.254.1.0 will show it)

any suggestions?

Thanks,
Jim

_______________________________________________
cisco-nsp mailing list  cisco-nsp at puck.nether.net
http://puck.nether.net/mailman/listinfo/cisco-nsp
archive at http://puck.nether.net/pipermail/cisco-nsp/