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juergenm
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Advertisment BGP with same AS number

Mon Jan 15, 2018 10:10 pm

I have a prblem, i am announcing from a cisco with same as number to a mikrotik with have also same as number to an other AS.

The mirkotik dont announce the prefixes, if its not in the bgp networks table. The Cisco have it already in the network table and announce to mirktoik.

If I put the prefix in the mikrotik networks table, than the Mikrotik always announce it .. but normal he should only announce it, if he have a connection to the Cisco BGP Router ...

How I can solve this?
 
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Anumrak
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Re: Advertisment BGP with same AS number

Fri Mar 23, 2018 4:01 pm

Post a scheme pls.
 
markmcn
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Re: Advertisment BGP with same AS number

Fri Mar 23, 2018 6:27 pm

Hi juergenm
Without a diagram show the network lays and the issue it's hard to be sure.
But it sounds like you have and iBGP peering between the cisco and mikrotik, and an iBGP peering between the Mikrotik and some other router. (iBGP meaning they have the same AS number)
If this is the case it sounds like you are hitting a design feature of iBGP where "An iBGP peer will not readvertise an iBGP learned prefrix to other iBGP peers" This is to prevent loops. The correct way to do iBGP is to use a route reflector or to do a full mesh between all iBGP peers.
As I said I'm having to guess based on your inital description but this is what it sounds like.
Hope this helps.
Mark

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