Solved: Over riding local preference for BGP

wgranada1 · ‎04-24-2008

I have a issue here currently I have a BGP connection one in Dallas and the other in Ft. Worth. The way it is set up is that Ft. Worth is the primary and Dallas is the back. So I have local preference set up on the Dallas router so that traffic will go out Ft. Worth and if Ft. Worth is gone then traffic will reroute through Dallas. The issue is on the Dallas router I have set up another BGP connection but due to the local preference that is already there I can see that my routing table for this particular ip address 205.248.197.209 bounce between Ft. Worth and Dallas. I thought I could remedy this by using a route filter but it still isn't working is there any way I can over ride this?

Richard Burts · ‎04-25-2008

Warren

The additional information does show that you are receiving an advertisement for the /32 route from that neighbor (among others). And it does not show the weight being applied. In thinking about why it does not show with weight I wonder if it was learned before you applied the weight. Would you do a reset on that neighbor to relearn the prefixes advertised by the neighbor and then do sh ip bgp 205.248.197.209 and post the output.

HTH

Rick

HTH

Rick

View solution in original post

Richard Burts · ‎04-24-2008

Warren

In general I would think that if you were to configure weight on the new BGP connection in Dallas then Dallas would be able to use those routes since weight is earlier in the BGP decision process than local preference.

If that does not seem to solve your issue then perhaps you could provide some additional details of how BGP is configured on both routers.

HTH

Rick

HTH

Rick

lamav · ‎04-24-2008

Warren:

Weight is a Cisco-proprietary BGP attribute, so if you're working in a multivendor environment you should work with another attribute to influence path selection.

Victor

wgranada1 · ‎04-24-2008

Thanks guys for the info but the other end is a cisco as well I tried using weight but I think I'm doing it wrong as it didn't work. Trying to find some docs on it now.

Richard Burts · ‎04-24-2008

Warren

Weight should work. Perhaps you can post what you have configured and we can suggest how to improve it.

HTH

Rick

HTH

Rick

wgranada1 · ‎04-24-2008

Thank you for the help, the one in blue is the new BGP connection I've added today. Sorry I took off the weight statement as when

I did it it didn't work so I removed it.

Richard Burts · ‎04-24-2008

Warren

I looked at what you posted. But without seeing how you had attempted to configure weight, we can not know why it did not work.

It might also be helpful to see the prefix list that is applied to these neighbors.

HTH

Rick

HTH

Rick

wgranada1 · ‎04-24-2008

ok I think all I did for the weight statement was add:

neighbor 168.162.60.209 weight 200

here is everything....

Richard Burts · ‎04-25-2008

Warren

Thanks for the additional information. This looks reasonable. The routes learned from that neighbor should have weight applied. And the prefix list does permit 205.248.197.209/32. Are you sure that the neighbor is advertising this as a /32?

It would be helpful if you have the weight command in the config to post the output of show ip bgp 205.248.197.209 and of show ip route 205.248.197.209.

HTH

Rick

HTH

Rick

wgranada1 · ‎04-25-2008

Hi Rick thank you for taking the time to look into this here are the show commands as requested. For the weight command it is already in there unless I did it wrong. Please see attached for the output commands

as a work around I have added static routes till we figure this out.

Richard Burts · ‎04-25-2008

Warren

The additional information does show that you are receiving an advertisement for the /32 route from that neighbor (among others). And it does not show the weight being applied. In thinking about why it does not show with weight I wonder if it was learned before you applied the weight. Would you do a reset on that neighbor to relearn the prefixes advertised by the neighbor and then do sh ip bgp 205.248.197.209 and post the output.

HTH

Rick

HTH

Rick

wgranada1 · ‎04-25-2008

Hi Guys;

Thank you all for your help!!!! I don't know what the difference is between now and yesterday but I reset the routes again and now I its going over the right way. Thank you agian for all your help....here is the output after I reset BGP:

sfschirt4#sh ip bgp 205.248.197.209

BGP routing table entry for 205.248.197.209/32, version 92997

Paths: (4 available, best #2, table Default-IP-Routing-Table, Advertisements suppressed by an aggregate.)

Not advertised to any peer

Local

172.19.200.4 (metric 5) from 172.19.103.30 (172.19.103.30)

Origin incomplete, metric 1, localpref 100, valid, internal

64940

168.162.60.209 from 168.162.60.209 (168.162.60.209)

Origin IGP, localpref 100, weight 500, valid, external, best

Extended Community: RT:7381:4169

64940, (received-only)

168.162.60.209 from 168.162.60.209 (168.162.60.209)

Origin IGP, localpref 100, valid, external

Extended Community: RT:7381:4169

64940, (received & used)

168.162.60.213 from 168.162.60.213 (168.162.60.213)

Origin IGP, localpref 100, valid, external

Extended Community: RT:7381:4169

t814687 · ‎04-25-2008

What's the origin of this host route? OSPF, right? Can you sh ip route and sh ip bgp for your other router? It looks like eBGP feeds back the route back to you..it should not as AS PATH should prevent that...

serg

wgranada1 · ‎04-25-2008

Thanks Serg for chiming in as well I appreciate your assistance