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BGP Router ID/Neighbor Address

So I am posting this because I can't seem to wrap my head around it.  It is the first time I have ever seen something like it before and while I will admit that my experience is limited I was not aware that this was possible or how it works.  I am using different ips than what is on my network but everything else was cut and pasted.  Please see below.  Can someone explain why or how it works with the router ID being the same as the neighbor address.  I didn't think this was possible.


router bgp 65102
bgp router-id
bgp log-neighbor-changes
network x.x.x.0 mask
network x.x.x.0 mask
neighbor remote-as 13979
neighbor allowas-in
neighbor soft-reconfiguration inbound

Julio E. Moisa
VIP Mentor


Please correct me if I understanding wrong the question, but It can work being the same address (except if 2 or more routers have the same router-id) , probably the router-id is a loopback IP and the BGP peering is being created with the loopback known through a NLRI like RIP, EIGRP, OSPF, ISIS, etc or static routing. Once the BGP process is created it will create an identifier with a valid IP, so you could select your own ID as well to avoid leave it randomly.



>> Marcar como útil o contestado, si la respuesta resolvió la duda, esto ayuda a futuras consultas de otros miembros de la comunidad. <<
Harold Ritter
Cisco Employee

Hi Brandon,


IOS only checks that the router ID is a valid IP address, hence why it works for you. 



Harold Ritter
Sr Technical Leader
CCIE 4168 (R&S, SP)
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