BGP.... primary / secondary Control at spoke site

[dpugalendi.d]

Dear All,

In the HUB.... Router Side due to AS prepond... Link1 is primary and Link2 Is secondary for all the spoke sites Routing.

But I need at one specific spoke site... Link2 should be primary and Link1 as secondary....

By what local BGP commands we can make the spoke site as required.. Thanks in advance

[hkkalra]

Hi,

Can you share your configuration with us or a sample configuration so that we understand the exact application of AS-Path prepend that you are using in your Network. As per my understanding AS-Path prepend is used in a route-map and then the route-map is applied with the specific neighbor. So you can specify to which neighbor you want to advertise the routes with the prepended ASes. You can simply remove the route-map from the Neighbor and add the same for Link 1 on the respective router.

If you can share some part of the config with a little detailed explanation we can help you make a sample config to achieve this. Also find a sample config below.

router bgp 1

neighbor 1.1.1.1 remote-as 4

neighbor 1.1.1.1 update-source loopback0

neighbor 2.2.2.2 remote-as 5

neighbor 2.2.2.2 update-source loopback 0

neighbor 2.2.2.2 route-map AS out

!

!

route-map AS permit 10

set as-path prepend 1 1 1 1 1

This configuration will make sure that all the routes this router advertises to neighbor 2.2.2.2 is using prepend and adding it's own AS 5 times to the route advertisement.However there will be no change in the route advertisement to neighbor 1.1.1.1.

Regards,

HK 

[hkkalra · Accepted solution]

Hi, 

Just left one thing on my earlier post. In case the Prepend is being used on the Hub side and you want to control the route selection on the spoke side. In that case using "weight" command would be a good option. As this is a Cisco Specific Parameter and if used this is given highest priority from all the other attributes.

router bgp 1

neighbor 1.1.1.1 weight 500

Please find a detailed explanation of this on the following link. 

http://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/26634-bgp-toc.html#weight

Regards,

HK

[dpugalendi.d]

 HUB to spoke is using Link1 becz of AS Path prepend

Spoke to HUB is using Link2  - becz of weight command

Asymmetric routing - happening now , how to make this symmetric - ( my HUB is single link for all the 10 Spokes )

[hkkalra]

Hi

Please share your topology. 

Regards, 

HK