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Community Member

BGP optional parameters

Hi All,

Attached is packet capture of the BGP on 192.168.10.1 router.

bgp.jpg

The the config of the 192.168.10.1 (Packet number 23) 

router bgp 400

bgp router-id 192.168.10.1

bgp log-neighbor-changes

bgp default local-preference 150

network 10.0.0.0/15

network 10.2.0.0/15

network 10.250.0.0/15

network 10.252.0.0/15

redistribute connected

redistribute static

neighbor 192.168.10.5 remote-as 65000

neighbor 192.168.10.5 weight 1

neighbor 192.168.10.5 soft-reconfiguration inbound

neighbor 192.168.10.5 route-server-client

The BGP peers are not forming between the two Routers. The router 192.168.10.5 is ISP and we do not have control over it.

Is there a way to remove optional parameters from the packet 23 or any configuration changes are required from the above config to remove the optional parameters.

Or is there any other issue which I am overlooking.

Your assistance will be highly appreciated.

Regards,

Ravindra K

11 REPLIES
Silver

BGP optional parameters

Look at the notification message.

Is there really a need for last line 'route-server-client' ?

Thanks.

Community Member

BGP optional parameters

Hi Rais,

Not really. But does that add parameters to the BGP optional parameters.

Regards,

Ravindra K

BGP optional parameters

Hi,

is the BGP session failing? Or you just don't exchange any prefixes with the neighbor?

As Rais is suggesting, I'd try to remove the 'route-server-client' command from your config, as it can be modifying the AS_PATH of your prefixes advertised considerably, see

http://www.cisco.com/en/US/docs/ios/ios_xe/iproute_bgp/configuration/guide/irg_route_server_xe.pdf

HTH,

Milan

Community Member

BGP optional parameters

Yes Milan,

Its failing. I am giving it a go in the lab. Will keep you all updated.

Regards,

Ravindra K

BGP optional parameters

Hi,

in you packet capture, are there any details visible in the BGP Notification message?

Have you tried to remove the

route-server-client

command from your config?

BR,

Milan

Purple

BGP optional parameters

Hi,

you received a notification message which should have appeared in the logs and which is in your capture file can you tell us what it is fussing about because when there is a mismatch in supported capibilities it doesn't bring the neighborship down.

Regards.

Alain

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Community Member

BGP optional parameters

Hi Cadet,

My requirement is that I do not want the optional parameters to be part of my config. Please let us know what configs should I eradicate from the config.

Thanks.

Ravindra

Purple

BGP optional parameters

Hi,

neighbor dont-capability-negotiate

Regards.

Alain

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Community Member

BGP optional parameters

Hi Cadet,

Do you mean the relatationship does not come down when optional paramters are not same?

We saw one more error of the AS bit. The opposite brand supported only 2 byte ASN so it used to send warning.

Please explain the behavior and the use of optional parameters.

Regards,

Ravindra K

Purple

BGP optional parameters

Hi,

I mean that it is a negotiation and if a bgp speaker sees acapability as not supported by the peer with a notification message then it will try to bring up the peering again this time not sending this capability but it should not bring the neighborship down.

But in your case apparently the peer has no optional parameter so maybe  this is why it won't bring the neighbourship up and that's why I proposed the command  I found in my previous post.

Regards.

Alain

Don't forget to rate helpful posts.
Community Member

BGP optional parameters

Hi Cadet,

It makes sense.

the behavior which we have seen was that the peers were failing so we captured the logs (pcap above). But we lost the access after removing the route-server-client command as we were connected on the WAN IP address.

We found that opposite brand has advertised a default static route. So which means that the command route-server-client did work.

We used prefix list to stop the default route being advertised to our router.

and it worked fine. Considered this as closed and you guys saved my day.

Thank you very much.

Regards,

Ravindra

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