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Beginner

eBGP Peer not Establishing

Hello everyone,

 Topology

I have built the below lab in my spare time and very briefly here is an explanation:

The main routing is done via OSPF apart from 2 BGP Routers circled in Blue on the outer sides.

The OSPF routing works absolutely fine and I am able to ping every interface form every other interface. I intend to have BGP peer over the OSPF network.

Configured on the 2 BGP Routers (R10 and R11) are Static Routes telling them that to contact the other BGP router they must pass through the next hop.
2018-01-15_12h34_41.png

 Problem

The problem I have is that I cannot establish a peering between the two BGP Routers over OSPF.

They both constantly fluctuate between the 'Idle' and 'Active' states.

Troubleshooting Done

From my research (I used this site to see the different BGP states), these states indicate that a TCP session cannot be successfully established.

After running Wireshark on both interfaces involved with R10, I did notice that there were some inconsistencies with the TCP packets:2018-01-15_12h48_44.png

 

I am no BGP/Wireshark expert but I do think this indicates that the TCP is unable to be established.

Note that the BGP Routers are unable to ping the inside interfaces of the OSPF interfaces. I do think that this is also a major factor but I cannot figure out why.

I would kindly appreciate any assistance with my configuration and if you need any of the outputs please let me know.

Everyone's tags (4)
2 REPLIES 2
Cisco Employee

Re: eBGP Peer not Establishing

Hi Tariq,

two quick questions to understand your setup:

 

  1. did you advertise e0/0 address space of your e-BGP routers inside Ospf ?
  2. did you configured your BGP session with the ebgp-multihop feature ?

thank you

Beginner

Re: eBGP Peer not Establishing

Hi Pigallo,

To answer your questions:

  1. Yes I did. I advertised that entire subnet (on both Routers) within the entire OSPF process
  2. Yes I did. I figured out that the problem was me setting the multihop to 2 instead of 5 as I should have

Hope that helps.

Also please note that this topic is a duplicate of the original topic here where the issue is solved.

 

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