BIG problem...please help! 2

[gsmserv]

I'm just starting in CISCO routers and I have a problem...I know this may seem easy to you but I can't solve it. Here's the problem:
I have the following router configuration:

router bgp 65008
network 10.8.0.0/16
neighbor 192.168.8.1 remote-as 65254
neighbor 192.168.8.1 ebgp-multihop 255
neighbor 192.168.8.4 remote-as 65003
neighbor 192.168.8.4 ebgp-multihop 255
neighbor 192.168.11.1 remote-as 65013
neighbor 192.168.11.1 ebgp-multihop 255 !
line vty

show ip bgp ipv4 unicast 10.129.0.0/16
BGP routing table entry for 10.129.0.0/16
Paths: (3 available, best #2, table Default-IP-Routing-Table)
Advertised to non peer-group peers:
192.168.8.1 192.168.11.1
65013 65254 65047 65129
192.168.11.1 from 192.168.11.1 (192.168.13.2)
Origin IGP, localpref 100, valid, external
Last update: Mon Aug 8 00:33:07 2005

65003 65003 65003
192.168.8.4 from 192.168.8.4 (192.168.136.2)
Origin IGP, metric 0, localpref 100, valid, external, best
Last update: Tue Aug 2 15:46:39 2005

65254 65047 65129
192.168.8.1 from 192.168.8.1 (192.168.200.3)
Origin IGP, localpref 100, valid, external
Last update: Sat Aug 6 04:59:11 2005

And here is my problem:
What do I write in the CISCO CLI to make the third path the "best" for the router. In other words I want the word "best" to be on the third path!
Hope you guys can help (soon)!
Thanks!

 

[gsmserv]

Common please help!!!
I beg you!

 

[PalmTest]

Have you checked the Cisco site?

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094934.shtml

Make sure that the third path has a better metric.

HTH

 

[jneiberger]

If you always want 192.168.8.1 to be the preferred path for this router, add the following statement:

neighbor 192.168.8.1 weight 10

The number you assign to the weight makes no difference right now. It's enough that a weight of 10 is greater than the weight assigned to the other neighbors, which is zero.

I would HIGHLY recommend that you learn BGP as quickly as possible or find someone who knows it well. It's very easy to screw things up if you don't know what you're doing.

Good luck!
John

 

[gsmserv]

ok...I need to do the following: for the other two routes I need to insert more hops so the preffered route I need to use (the third one) is the most cost effective. Any ideas? or suggestions? or documents? HELP!

 

[jneiberger]

Does this change need to affect the routing behavior of other routers or just this router? Are your other routers running iBGP? Based on your config, it looks like you don't have any iBGP neighbors. If that's the case then the solution I gave you will work.

Can you be more specific about what problem you're trying to solve?

 

[gsmserv]

ok...I'll be more specific.
That is the configuration of a router in Canada. I have to solve the problem from my office wich is in Romania. So I don't have access to the router in canada. If I use the weight option it will damage the other two paths. As you can see the second path has three fake hops so that the third path will be the preffered one. But that didn't happen...the second path is still the best. So if I create another fake hop for the second path (the first path already has 4 hops) the third one will be the best. If anyone can find another solution to this problem...

 

[jneiberger]

The 2nd and 3rd routes have the same number of ASes in their AS path. Try adding one more to the second one. You could also try decreasing the local preference on routes learned from the first two peers.

 

[gsmserv]

how do I do that?
How do I add another one to the second path...or...how do I decrease local preference on routes learned from the first two peers. I'm now studying BGP configuration but it's pretty hard...tell me what to write plz!

 

[jneiberger]

I hesitate to tell you exactly what to write because I don't have access to all of your configs, your network diagram, or your routing policy. Basically, you need to create a route map that sets the local preference and then apply it to the two appropriate neighbors.

It will look something like this:

router bgp 100
neighbor 10.1.1.1 remote-as 200
neighbor 10.1.1.1 route-map mymap in

route-map mymap permit 10
set local-preference 200

Look up route maps and BGP on

http://www.cisco.com.

There are a lot of examples. You really need to make sure you understand the consequences of your actions before you change the configurations.

Look here:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fipr_c/ipcprt2/1cfbgp.htm

You can be more granular with your route map if you only want to apply the local preference to certain routes instead of all routes learned from that neighbor.

 

[gsmserv]

ok...if I want to add a another hop to the second path I just write:
neighbour 194.168.8.4 next-hop-self
That would solve the prblem...but what if I wanted to add two hops to the second path? What do I write? how do I do it?

 

[jneiberger]

No! Next-hop-self is for something entirely different.

You'll need to use a route map no matter what you want to do. If you want to change the local preference then use "set local-preference" in the route map. If you want to pad the AS path then use "set as-path prepend 65003 65003 ..."

I would try using local preference first. You *really* need to read the relevant sections of the link I sent. You can really mess things up if you don't know what you're doing.

It's much easier to shoot yourself in the foot with BGP than with other routing protocols, and there's always the chance that you'll blow your entire leg off.

 

[peterd51]

Hi,

if you're not sure of the outcome on a remote router...

then I'd strongly recommend using 'reload in 20'.

This will force the router to reboot in 20 minutes unless you issue a 'reload cancel' command. You can give a different number of minutes but I find 20 is a good figure to use.

The idea is, you set up the router to reload in 20 minutes, then change whatever it is you're playing with.

If you lock yourself out of the router then it'll re-boot to the original config and if you still have access to it after your recent change then you can cancel the re-load and then save the new config.

Regards
Peter

 

[gsmserv]

Ok...so..."set as-path prepend 65003" works just great...but I need another way...can't do it with the "set local-preference" option because all the advertised routes that go through the second path would have increased local-preference. I don't quite know if I explained this right but...
Any other ideas on how to make the third path the prefered one?

 

[jneiberger]

Why do you need another way to do it if AS path prepending is working for you?

 

[gsmserv]

because I would love to have more then one option I can count on...

 

[jneiberger]

There are a number of ways to do it but they all involve playing around with BGP attributes and metrics using route maps.

 

[gsmserv]

ok...I don't need the exact solutions or what to write...but give me some hints. For example...
And I'll look into it...anyway, I'm starting to understand BGP but there's a long way to go.

 

[jneiberger]

Learn about BGP attributes and the BGP route selection process. Once you understand that, it's easier to see how you can manipulate those attributes to enforce your routing policies.

There are a number of ways: increase the weight on a peer, increase the local preference, decrease the MED (or increase the MED on all other routes), etc.

 

[gsmserv]

I have a question...I used set as-path prepend 65003 and now the preffered route is the third one...now the question...if I type show running config what will I see? How will the "running config" screen look like?