[c-nsp] bgp config [continue]

[Anton Yurchenko]

Shaun Reitan wrote:

>I'm setting up bgp between me and a guy I know.  On his end he has a
>connection with Cox and then has a DS3 running to me.  The connection with
>Cox is his primary connection and only wants to use the ds3 as fail-over.  I
>setup bgp and for the most part it looks like it's working but there are a
>few problems I'm running into.  First alittle run down, I am only sending a
>default 0.0.0.0 route, and he is only receiving a default 0.0.0.0 route from
>both me and his other provider.  On my nei he has a route-map called backup
>set on out.  The only thing in this route-map is a as-path prepend with his
>asn 3 times.  He also has route-map on COX called local-pref set on in.
>local-pref only has a set local-preference 200 in it.
>
>The problems i've been having are the following.
>
>When turning bgp up the first problem I see is that customers in my address
>space cannot trace to his address space, they can ping.  I think I narrowed
>this problem down, I think what is happening is that my route see's his ip
>space as bring across the ds3 (a sh ip bgp shows his ip space having a *> to
>his side of bgp nei) and sends the packets across the ds3, but then his
>router listens to the route-maps and sends back across Cox.  A few reasons
>why I think this, 1 being that if I set a static route on his router routing
>my ip space back through the ds3 it solves the problem.  Second being that
>pings shows 17ms rather than 1ms I get when the static route is in place.  A
>few have told me just to leave the static route in place but that seams half
>assed to me.  If the ds3 is ever down then bgp would route around it.
>
>  
>
He is announcing you his network and this is why you are able to use DS3 
to reach him, but you are only announcing him the default. In his 
routing table he has a more specific path to your network through his 
ISP that is why he uses it. To fix this announce him default and your 
network.

>Another problem, my providers upstream is global crossing and internap, on
>gblx's route-server when my bgp session is down I see Cox's paths, but as
>soon as I turn up bgp those paths disappear and gblx only shows the path
>through me.  Not only that but gblx doesnt seam to listen either to the
>route-maps and still sends traffic to my provider which also forwards it to
>me.
>
>  
>
When he starts announcing his network to you, you also propogate this 
announce to GBLX, so they install it into their tables, because his 
network has a shorter path through you, then other paths that they have. 
This is normal, to make the path through you look less preferable, you 
need to announce his network with prepends, number of prepends that will 
do the job may vary.

>I highly doubt my provider and gblx both have problems with there config so
>I'm assuming it's my config or the router config at the other end of the
>ds3.  Any advice?
>
>Some of you may find info your looking for on my previous post at
>https://puck.nether.net/pipermail/cisco-nsp/2005-July/022343.html
>
>
>~Shaun
>
>
>
>_______________________________________________
>cisco-nsp mailing list  cisco-nsp at puck.nether.net
>https://puck.nether.net/mailman/listinfo/cisco-nsp
>archive at http://puck.nether.net/pipermail/cisco-nsp/
>
>  
>