BGP router-id change without any effect

[johnyoon75]

Hello.

This is john.

How can i change bgp router-id without any effect?

I have to change bgp router-id because interface ,which is used current bgp router-id, does not use anymore.

Regard,

John

[Harold Ritter]

The change of the RID will necesseraly lead to BGP sessions resets. This is why best practice recommends nailing the RID with the "bgp router-id" command and that this address be associated with a loopback interface address.

Hope this helps,

[johnyoon75]

Thank you for response.

As you told me, If i change bgp router-id, all bgp session would be reset.

So i am considering how can i accomplish without any effect on bgp or decrese effect....

In situation, If i configure "weight" command to neighbor, Does any side effect will take?

Regard,

John

[Harold Ritter]

The weight only has local significance. It will not help since all local sessions will be reset. Can you tell us more about your topology.

Thanks,

[steve]

Assuming you have one BGP speaking router, you could weight your traffic to your "secondary" provider, prepend AS paths to your "primary" provider, then do a soft reset on both links.

After you verify that most/all of your traffic is going through the "secondary" provider, you would make your BGP changes on the "primary" connection.

Then undo your previous changes and allow traffic to flow back through your "primary" provider.

Hope this helps,

Steve

http://www.cisco-forum.com

[Harold Ritter]

This will not help in changing the RID though. As I stated in my previous post, if you force a change of RID by configuring a loopback interface and the "bgp router-id" command, both sessions would be reset at once, in which case the weight doesn't help at all.

Hope this helps,

[johnyoon75]

Thank you for response.

I'm gonna explain more detail.

There four routers running eBGP and iBGP in my company.

r1 and r2 have eBGP connection with ISP_1, also have iBGP conection with r3(iBGP peer), and r4(iBGP peer).

r3 and r4 have eBGP connection with ISP_2, also have iBGP connection with r1 and r2.

r1 knew specific route(examle, 10.10.10.10) via r3 because of bgp router-id. bgp router-id of r3 lower than r4. all other value the same(weight, local preference, as path etc...)

One day, r3 had removed interface(3.3.3.3) which was used bgp router-id by r3 and neighbors. the interface didn't exsit anymore. But the thing is that all neighbor(r1, r2) still know 3.3.3.3 for neighbor's router. As i told you, all other attribute to select bgp route are same. at last, r1 select path via r4 because of lower bgp-router id.

So I have to recovery traffice route from r4 to r3.

because r3 shoud be roll primary route path.

At this time, i tried to change bgp router-id.

As you know, If i change bgp router-id, all neigbor session could be reset.

Thus, i consider changing weight to neigbor.

If i change weight, bgp neigbor session doesn't reset, although bgp table may be reset...

I'm curiout about that..

How can i choice bot of them...

I want to reduce changing impact smaller...

Additionally, When i chanege weight, Does any side effect in our network...?

Please let me know....

Regard,

John.

[johnyoon75]

Additional question.

Do you have idea about bgp convergence time

when i change router-id or weight for neighbor.

Regard,

John