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Krisken
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BGP issues...

Mon Apr 25, 2022 2:03 am

So, I got 3 Mikrotik CHR routers on 3 different locations :
- Netherlands, Meppel
- Netherlands, Wormer
- Germany, Frankfurt

I have created a GRE connection between all of them, and now I want to do BGP over it.
My BGP connection between Frankfurt and Meppel is up and running. The BGP connection between Frankfurt and Wormer is also up and running.
The only issue is the BGP connection between Wormer and Meppel doesnt work at all. I tried various things, nothing helped me out.

Anyone that can take a look at this issue?

Router Meppel (https://photos.app.goo.gl/Z4nZsLTbv17qiCbx9)
- As you can see, I can ping Frankfurt (10.251.0.2) over the GRE tunnel
- As you can see, I can ping Wormer (10.251.0.6) over the GRE tunnel
- Only the BGP with Frankfurt is up and running
- The BGP session with Wormer isn't even there (but is configured!)

Router Wormer (https://photos.app.goo.gl/HB3g6Q8ZtYnhnmLz7)
- As you can see, I can ping Frankfurt (10.251.0.9) over the GRE tunnel
- As you can see, I can ping Meppel (10.251.0.5) over the GRE tunnel
- Only the BGP with Frankfurt is up and running
- The BGP session with Meppel isn't even there (but is configured!)

Router Frankfurt (https://photos.app.goo.gl/jks4BFKRAG9Ei8gq7)
- As you can see, I can ping Frankfurt (10.251.0.10) over the GRE tunnel
- As you can see, I can ping Meppel (10.251.0.1) over the GRE tunnel
- Both BGP sessions are up and running

Any idea and advice is welcome! I know, I don't have filters on those internal IP's at all, I tought that this could (maybe) be the problem...
 
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Re: BGP issues...

Mon Apr 25, 2022 2:47 am

It looks like your issue is iBGP split-horizon.

Essentially, when peering within the same AS, you need full mesh peerings which means every router must peer with every other router

Alternatively, you can turn on route reflection at the router in frankfurt.

This will give you some background
https://www.rfc-editor.org/rfc/rfc4456#section-4
 
Krisken
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Posts: 135
Joined: Thu Oct 25, 2012 11:35 am

Re: BGP issues...

Mon Apr 25, 2022 2:51 am

When peering within the same AS, you need full mesh peerings which means every router must peer with every other router
That's exactly what I try to achieve :-)
Thanks for your (very fast) answer!

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