BGP Prevent Transit AS

This topic is to discuss the following lesson:

Many thanks for the lesson, it’s very easy to understand!

What about this method, Rene?

access-list 1 permit

route-map NO-EXPORT permit 10
  match ip address 1

neighbor route-map NO-EXPORT out
neighbor route-map NO-EXPORT out

Ofc we can use “match ip address prefix-list” as well. And my deepest respect for all what you do for us all.

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An access-list will work as well, no problem at all :slight_smile:

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Nice!!! It cleared my questions!!! Thanks a ton!!!

You are welcome Ulhas.

Hello Rene,

I have gone through many topics in this website and that cleared my idea as well but I don’t see any note regarding Multiple Spanning-Tree Protocol.
If you share some labs/note for MSTP will be helpful for me to understand it better.

Thanks a lot.

Thanks a million Rene!! I really appreciate you sharing your knowledge, this really helped me out a lot.

You are welcome Marcus!

Hello Arijit,

I’m glad to hear that you like it. I’ll add some MST material in the future!


You have really cleared the air on some difficulties i was having.
Really self explanatory.
Thx Renee

This really helped me :slight_smile:
Thanks a lot Rene

Nice and neat, i like it :slight_smile:


Nice and clear explanation of all the complex BGP terms.
Great lesson to understand key features of BGP.


Thanks Hamood


I would appreciate if you can talk about how to advertise routes toward inside your network.

let say you have r1 and r2 are mutihome. R1 to isp1 and R2 to isp2 (getting bgp full table). Now let say you have R1 and R2 criss cross connected to nexus 7k inbound. I know you can run iBGP but that would be too many routes to your switches. What would be a good solution in this situation?


Hi Nav,

If R1 and R2 are the only exit points for your network then a default route will do the job, no need to run iBGP on all your internal devices.


Hello Rene,

Great job as always, it is possible if you publish the routers configurations? I would like to see how you did the configuration, this also helps me clearing the theory.

It’s just a question.

Thank you very much!!

Hi Diana,

Do you mean the startup configurations?

In the most recent lessons I have been adding the final configurations, for example:



Rene – in your example of Filter-list with AS PATH access-list you wrote:

R1(config)#ip as-path access-list 1 permit ^$

Is the AS number of R1 suppose to go between the ^ and the $? In your example you didn’t specify an AS # - let’s just say R1 AS # is 4444. Should it look like this?

R1(config)#ip as-path access-list 1 permit ^4444$