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New Member

iBGP problem - how to pass eBGP route to other iBGP neighbor?

Dear all,

I have 3 routers (RT01, RT02 and RT03) running iBGP (AS-1001) and Each router connects to a eBGP neighbor(RT-A, RT-B and RT-c). (topology is as attached PNG file)

Problem I encounter is:

RT01 can get routing information from RT02 itself and RT-B(AS-1003)

RT03 can get routing information from RT02 itself and RT-B(AS-1003)

RT02 can get all routing information from both RT03 including RT-C and RT01including RT-A

but

RT01 can not get routing information from RT03 including routing from RT-C(AS-1004)

RT03 can not get routing information from RT01 including routing from RT-A(AS-1002)

I think it is because RT02 does not advertise routing information which is learned from one neighbor to another iBGP neighbor. (i.e. RT02 does not pass routing learned from RT03/RT-C to RT01, and also does not pass routing learned from RT01/RT-A to RT03)iBGP.png

any advice how to resolve it will be appreciated. Thanks!

  • WAN Routing and Switching
Everyone's tags (1)
4 ACCEPTED SOLUTIONS

Accepted Solutions
Purple

iBGP problem - how to pass eBGP route to other iBGP neighbor?

Hi,

in your AS 1001, just do a full mesh of iBGP neighbours: r1-r2,r1-r3,r2-r3

Regards

Alain

Don't forget to rate helpful posts.

Don't forget to rate helpful posts.
New Member

iBGP problem - how to pass eBGP route to other iBGP neighbor?

You have to use a iBGP full mesh, or configure R2 as route-reflector.

bests

stefano

New Member

iBGP problem - how to pass eBGP route to other iBGP neighbor?

stefano and alain are correct,

bgp rules state an ibgp neighbour will not advertise ibgp learned routes to another ibgp peer, (without the above suggestions or confenderations)

Regards Neil 

http://uk.linkedin.com/pub/neil-grant/20/5b0/267

Regards Neil http://uk.linkedin.com/pub/neil-grant/20/5b0/267
Silver

iBGP problem - how to pass eBGP route to other iBGP neighbor?

There is not really much else to add to what has already been stated, but I did find a link that may help provide more details:

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a00800c95bb.shtml

5 REPLIES
Purple

iBGP problem - how to pass eBGP route to other iBGP neighbor?

Hi,

in your AS 1001, just do a full mesh of iBGP neighbours: r1-r2,r1-r3,r2-r3

Regards

Alain

Don't forget to rate helpful posts.

Don't forget to rate helpful posts.
New Member

iBGP problem - how to pass eBGP route to other iBGP neighbor?

You have to use a iBGP full mesh, or configure R2 as route-reflector.

bests

stefano

New Member

iBGP problem - how to pass eBGP route to other iBGP neighbor?

stefano and alain are correct,

bgp rules state an ibgp neighbour will not advertise ibgp learned routes to another ibgp peer, (without the above suggestions or confenderations)

Regards Neil 

http://uk.linkedin.com/pub/neil-grant/20/5b0/267

Regards Neil http://uk.linkedin.com/pub/neil-grant/20/5b0/267
Silver

iBGP problem - how to pass eBGP route to other iBGP neighbor?

There is not really much else to add to what has already been stated, but I did find a link that may help provide more details:

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a00800c95bb.shtml

New Member

Re: iBGP problem - how to pass eBGP route to other iBGP neighbor

Thanks all for prompt response and clear clarification.

Since RT01 locates in different site and is unable to do full mesh with other iBGP neighbors, I will study all the information you provided first and try to configure R2 as route-reflector as adviced.

Thanks!!

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