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Beginner

Ebgp neighbourship

I have configure 3 router R1, R2, R3 and configure ibgp in R1 and R2 and ebgp in R2 and R3 with EIGRP update source with loopback.  and advertise R3 loopback address  in network.. the problem is ebgp is up with R2 but after 3 minutes it down and sudden up and after 3 minutes it again down and it happened continously... what may be the problem. 

1 ACCEPTED SOLUTION

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VIP Mentor

Hi

Have you advertising any loopback (used for the ebgp peering) into BGP on R2 and R3?

If it is yes, the neighborship will be flapping because it will be including an entry on the routing table with AD 20 for the loopback (it will be preferred because is a lowest administrative distance than 90) but it will try to reestablish the neighborship with EIGRP and an entry with 90 will be displayed again into the routing table and the flapping will be displayed again.

My suggestion is not advertise the loopbacks used for the bgp peering known through the NLRI (in this case EIGRP), otherwise you should use the network directly connected between R2 and R3 and then advertise the loopbacks. 

Could you please share your config?

Thank you in advance. 




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

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3 REPLIES 3
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Collaborator

Hello,

Run debug ip BGP with terminal monitor to receive debug information.

Masoud

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VIP Expert

Hello,

3 minutes (180 seconds) is the default BGP hold timer, which means that a keepalive has been missed three times (keepalive should be sent every 60 seconds by default). Hard to say why this happens...can you post the configs of both R2 and R3 ?

Highlighted
VIP Mentor

Hi

Have you advertising any loopback (used for the ebgp peering) into BGP on R2 and R3?

If it is yes, the neighborship will be flapping because it will be including an entry on the routing table with AD 20 for the loopback (it will be preferred because is a lowest administrative distance than 90) but it will try to reestablish the neighborship with EIGRP and an entry with 90 will be displayed again into the routing table and the flapping will be displayed again.

My suggestion is not advertise the loopbacks used for the bgp peering known through the NLRI (in this case EIGRP), otherwise you should use the network directly connected between R2 and R3 and then advertise the loopbacks. 

Could you please share your config?

Thank you in advance. 




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

View solution in original post