Adjust Administrative Distance for Route Selection in BGP

[philippe_seror]

Dear all,

I am currently having many issues while ajusting administrative distance with specific BGP routes.

I am running one one of the latest IOS 15.6(3)M4 and i am not capable to modify the adminitrative distance of E-BGP specific received routes.

My objective is to prefer OSPF  over the BGP for only specific routes.

I have tried taking it from the BGP or OSPF side but still not working. the command "distance" is been taken by the router but without effect.

Actually i have filtered on inbound the E-BGP routes via routemaps & prefix lists but i would like to know if Cisco still supporting this feature . (Adjust administrative distance for specific routes)

The only command that actually works is the general adminitrative  distance settings that affect all routes within the mentionned protocol.

would someone be so kind to confirm me if the comming is comming from something i missed?

Attached a drawing of the actual configuration. I need to make sure that router SITE A will use sat Link to join SITE B instead of using the direct E-BGP link with SITE C.

Thank you in advance

[sivam siva · Accepted solution]

Hi 

Try this 

(config)#router bgp 100

(config-router)#network X.X.X.X mask Y.Y.Y.Y backdoor

To know about backdoor process use the below link.

https://community.cisco.com/t5/network-architecture-documents/what-is-the-bgp-backdoor-feature/ta-p/3154898

[philippe_seror]

Hi This is working thanks :)

Would you know why the "distance 111 x.x.x.x y.y.y.y" or "distance 111 x.x.x.x y.y.y.y ACL" would not work ? is it not supported anymore ?

[sivam siva · Accepted solution]

Hi

some platforms like 3000 NX-OS switches that have limited BGP capabilities, this method is not available.
and I would like to mention that It is done under the address-family (unicast, multicast or vrf) with the distance <AD> <neighbor> <wildcard> <optional ACL> command.
One problem with this method is that these prefixes will have their AD changed but BGP will still re-advertise them to any eBGP neighbors that have don’t have any inbound filtering. This can lead to asymmetrical routing for these routes because AD will only be changed locally.

[philippe_seror]

Hi sivam siva thank you for you quick reply, 

Understand better now the Idea.

However concerning my design i am using regex to advertize only the own AS to E-bgp Neighbors but I totally understand the point :)

[sivam siva]

Ok