BGP Flapping frequently

[Krishnendu AR]

BGP Flapping frequently in GNS3.

Please find the details attached.

Please advise how to get rid of this?

Krishna

[Krishnendu AR]

Im running BGP between R1 and R3 only.

-------------------------------------------------------------------

R3

AS200-R3#

*Mar  1 00:04:14.983: %BGP-5-ADJCHANGE: neighbor 1.1.1.1 Down BGP Notification sent

AS200-R3#

*Mar  1 00:04:14.983: %BGP-3-NOTIFICATION: sent to neighbor 1.1.1.1 4/0 (hold time expired) 0 bytes

AS200-R3#

*Mar  1 00:04:42.127: %BGP-5-ADJCHANGE: neighbor 1.1.1.1 Up

AS200-R3#

*Mar  1 00:07:42.439: %BGP-5-ADJCHANGE: neighbor 1.1.1.1 Down BGP Notification sent

AS200-R3#

*Mar  1 00:07:42.439: %BGP-3-NOTIFICATION: sent to neighbor 1.1.1.1 4/0 (hold time expired) 0 bytes

AS200-R3#

*Mar  1 00:08:16.675: %BGP-5-ADJCHANGE: neighbor 1.1.1.1 Up

-----------------------------------------------------------------------

R1

AS100-R1#

*Mar  1 00:07:42.319: %BGP-5-ADJCHANGE: neighbor 3.3.3.3 Down BGP Notification sent

AS100-R1#

*Mar  1 00:07:42.319: %BGP-3-NOTIFICATION: sent to neighbor 3.3.3.3 4/0 (hold time expired) 0 bytes

AS100-R1#

*Mar  1 00:08:16.571: %BGP-5-ADJCHANGE: neighbor 3.3.3.3 Up

AS100-R1#

[smitesh kharecha]

Hi Krishna,

Since you are using GNS, which operates on dynamips; I suggest you check out RAM and CPU utilization of your PC/Lappy when you are  running the above experiment.

If you find CPU utilization of your PC/Lappy is too high you need to adjust idlepc value. Search GNS forums for more info.

HTH,

Smitesh

[manju.cisco]

Hi Krishna,

I too tried your configs in gns3 in my PC and for me there is no flapping happening, bgp session is solid stable without any fluctuation........ i observed for 30mins

there is nothing wrong except your idle PC i believe.....

however, do add  "neighbor 3.3.3.3 update-source Loopback0" to have identical configs on both routers, that will be nice

[Krishnendu AR]

In which Router/IOS u tried?

Krishna

[Krishnendu AR]

AS100-R1(config)#router bgp 100

AS100-R1(config-router)#neighbor 3.3.3.3 up

AS100-R1(config-router)#neighbor 3.3.3.3 update-source lo0

AS100-R1(config-router)#^Z

AS100-R1#

*Mar  1 00:42:32.359: %SYS-5-CONFIG_I: Configured from console by console

AS100-R1#

*Mar  1 00:42:47.899: %BGP-5-ADJCHANGE: neighbor 3.3.3.3 Down BGP Notification sent

AS100-R1#

*Mar  1 00:42:47.899: %BGP-3-NOTIFICATION: sent to neighbor 3.3.3.3 4/0 (hold time expired) 0 bytes

AS100-R1#

*Mar  1 00:43:18.595: %BGP-5-ADJCHANGE: neighbor 3.3.3.3 Up

AS100-R1#

*Mar  1 00:46:18.951: %BGP-5-ADJCHANGE: neighbor 3.3.3.3 Down BGP Notification sent

AS100-R1#

*Mar  1 00:46:18.951: %BGP-3-NOTIFICATION: sent to neighbor 3.3.3.3 4/0 (hold time expired) 0 bytes

AS100-R1#

*Mar  1 00:46:45.527: %BGP-5-ADJCHANGE: neighbor 3.3.3.3 Up

AS100-R1#

*Mar  1 00:49:45.707: %BGP-5-ADJCHANGE: neighbor 3.3.3.3 Down BGP Notification sent

AS100-R1#

*Mar  1 00:49:45.707: %BGP-3-NOTIFICATION: sent to neighbor 3.3.3.3 4/0 (hold time expired) 0 bytes

AS100-R1#

AS100-R1#

AS100-R1#

*Mar  1 00:50:18.991: %BGP-5-ADJCHANGE: neighbor 3.3.3.3 Up

AS100-R1#

Still flapping

[smitesh kharecha · Accepted solution]

Hi Krishna,

Can you check the CPU and RAM utilization of the PC / Laptop you are using.

I'm sure it must be highly utilized.

Solution is to find the correct idlepc value. Search  the GNS forums and you will know how to find the correct idlepc value, as this is not the place to resolve the issue related to GNS.

HTH,

Smitesh

[Krishnendu AR]

CPU utiliztion is between 85-90%

I already have an Idle-PC s set for the router. Not sure why this happens?

Krishna

[smitesh kharecha]

Hi,

I would consider 85-90 % high when running  GNS. Also I'm seeing that 2 of your core is sometimes almost reaching 100%.

You need to find the best idelpc value. As per my experience, best one is found by reiterating the idelpc calculation number for time and each time check how much the utilzation is getting reduced.

As I suggested earlier, search the GNS forums for these tweaking as this is not a forum for those discussions (please don't take this as a rude comment).

Regards.

Smitesh

[Krishnendu AR]

Hi Smitesh,

Ill search the GNS3 forum to find out how to set the best Idle PC value.

Just wanted to make sure that there is no error in my config.

Krishna

[smitesh kharecha]

Hi Krishna,

Just a small one.

Add

neighbor 3.3.3.3 update-source Loopback0

to your R1, as Manju suggested above.

PS: Please close this thread if your concern is address, so that other community member doesn't waste their time coming to this post and finding it to be already answered.

Regards,

Smitesh

[Krishnendu AR]

Smitesh,

I have tried adding the update-source command to R1 . Still the issue persists.

Krishna

[smitesh kharecha]

Thats because in your case, root-cause is CPU high utilization; which can be only solved with the best idelpc value.

HTH,

Smitesh

[Krishnendu AR]

Sure, I'll try that out.

Thanks a lot for help Smitesh.

Krishna

[Krishnendu AR]

Hi Smitesh,

I just wanted to add one more point to this discussion.

I notied that only BGP neighborship is falppping between R1 and R3. However, EIGRP relationship between R1 and R3 is stable.

If it is because of high CPU utilization, isn't it should affect EIGRP also?

Krishna

Message was edited by: Krishnendu AR