Ask The Export: EBGP Remote AS Ping Failure

[syedaijazahmed48]

Dear Cisco Community,

I am reaching out for assistance with troubleshooting an EBGP (External BGP) configuration issue. I have followed the necessary steps and configured EBGP on all routers, but I am unable to ping the network reachable through the remote Autonomous System (AS).

I have reviewed the available resources and troubleshooting guides, but I am still encountering this issue. To assist with further analysis, I have included the relevant configurations of all routers and a diagram of the network topology. 

[MHM Cisco World]

Use redistrubte connect under bgp in all routers and try again 

MHM

[Harold Ritter · Accepted solution]

Hi @syedaijazahmed48 ,

All routers need routes to all of their eBGP neighbor addresses. The attached file doesn't show any static routes. 

Regards,

[syedaijazahmed48]

@Harold Ritter 

Thank you so much for your response.

If you do not mind could you please provide me with an example it will be really helpful to me and my concept will be clear

[Harold Ritter · Accepted solution]

Hi @syedaijazahmed48 ,

As an example you could configure the following static routes on R1:

ip route 2.2.2.2 255.255.255.255 12.1.1.2

ip route 3.3.3.3 255.255.255.255 13.1.1.2

It would also be better to configure neighbor statements only for adjacent ASes (i.e. for R1 only configure R2 and R3, for R2 only configure R1 and R4, etc)

In most real life cases, the eBGP session is established using the physical interface address, so ideally you would configure something like this:

R1:

router bgp 100

neighbor 12.1.1.2 remote-as 200

neighbor 13.1.1.2 remote-as 300

network 1.1.1.1 mask 255.255.255.255

R2:

router bgp 200

neighbor 12.1.1.1 remote-as 100

neighbor 24.1.1.1 remote-as 400

network 2.2.2.2 mask 255.255.255.255

R3:

router bgp 300

neighbor 13.1.1.1 remote-as 100

neighbor 34.1.1.1 remote-as 400

network 3.3.3.3 mask 255.255.255.255

R4:

router bgp 400

neighbor 24.1.1.2 remote-as 200

neighbor 34.1.1.2 remote-as 300

network 4.4.4.4 mask 255.255.255.255

Regards,

[syedaijazahmed48]

Dear Mr. Ritter,

I wanted to express my sincere gratitude for the guidance and support you provided me with my recent technical challenge. Your expertise and patience were instrumental in resolving the issue, and I am deeply thankful for your assistance.

Additionally, I would like to acknowledge the Cisco Community for fostering an environment where collaboration and support thrive. It's a privilege to be part of such a knowledgeable and helpful community.

Thank you once again, Mr. Ritter, and the entire Cisco team, for your dedication and hard work.

Warm regards,

Syed Aijaz Ahmed.

[Harold Ritter]

You are very welcome @syedaijazahmed48 and thanks for the excellent feedback