This is more of a cosmetic issue than an actual fault
I have 3 devices A, B & C.
A & B are ebgp neighbors, C & B are also ebgp nei
A sends 3 prefixes to B while C sends 1620 to B
B sends all 1620 + 3 routes to both neighbors A & C
I know BGP will forward learnt prefixes to peers and if peers see their AS number in the AS path they ignore the prefix.
My question: is there any way to stop B from sending back to A & C the prefixes it has already learnt from them? this will make troubleshooting much easier I guess.
{ 6 comments… read them below or add one }
Are A & C in the same AS ?
No, A is a WAN distribution device while B is my edge device peering with C which is my ISP edge device.
Then why should B advertise A’s routes back to A ? and the same question for C ?
That’s my question and how to stop this from happening as i only want to see in B’s advertise routes to C routes learnt from A and vice versa
Sorry, i shoud have been more specific. An EBGP peer does not advertise the networks it learns from one peer back to that same peer.
So if A advertises routes to B then B doesn’t advertise them back to A unless you have somehow setup a redistribution loop somewhere.
B should advertise A’s routes to C and C’s routes to A but not A+C’s routes to A & C.
How have you got this configured.
ad “An EBGP peer does not advertise the networks it learns from one peer back to that same peer.”
I know BGP works this way.
But I tried to find this statement in several documents and books and failed
Is it specified in some BGP RFC?
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