Strange ip cef behavior on Cisco 2951

[Boris Krajnc]

Hello.

I have 2 Cisco 2951 configured with HSRP. Everything woks fine, but after few hours ip cef stop working. If I try to disable ip cef (no ip cef) and enable again (ip cef), it wont start. If I reboot the router ip cef work again as expected. I have 300 users on this router.

My software version flash0:c2951-universalk9-mz.SPA.150-1.M6.bin.

Any sugestion would be helpfull

[balaji.bandi]

Look at some bugs reported :

https://www.cisco.com/c/en/us/td/docs/ios/15_0/release/notes/150MCAVS.html

if possible upgrade and check.

[Georg Pauwen]

Hello,

sounds like a bug...can you upgrade to release 15.7.3M3 MD ? Your 15.0.1 release is fairly outdated (2012)...
 

[Boris Krajnc]

Guys, thank you for your fast response. Bug was my first thought...... Unfortunately we don not have contract with Cisco , because we buy this device as refurbished.......

I have c2900-universalk9-mz.SPA.155-3.M5.bin, but i receive message that this software is not OK, for this device.

So....I can't do nothing :-(

[a.alekseev]

How did you decide that it's cef?

[Boris Krajnc]

I replace routers Cisco 2850 with 2951 and made redesign. I monitored old routers and I saw that CPU utilization was around 40 - 50%. When I replace routers with 2951 I saw that CPU utilization on new routers was + 90% and find that SNMP process was troublemaker. I shut down SNMP, and everything was OK - CPU between 20 - 30 %. after 5 hours CPU rise to 80% and regarding to the high traffic utilization rise and rise.

After deep research I find that ip cef is disabled - strange because I didn't change this in configuration. Like already said I try enable ip cef again but nothing happened. When I reboot the router and write command show ip cef I see that ip cef works fine and it is enabled. When ip cef work as should work than CPU utilization is around 20%.

My thought was also that something is wrong with router and I switched (HSRP) from Primary router to Secondary (where I saw that ip CEF  was OK). It works 8 hours and than ip cef stop working too (show ip cef return that ip cef is disabled). On both routers is the same software.

So I decide that something is wrong with ip cef.....

[balaji.bandi]

That good diag step you followed.

I am not sure, i were you, since you do not have Cisco contact to upgrade IOS,

use EEM Script to run, if ip cef disabled enabled back ( enable some logs see why this was going to disable)

Still think how come ip cef disables  automatically ?

some post for reference, again they have recommended to contact TAC

https://community.cisco.com/t5/routing/cef-not-running-even-though-enabled-globally/td-p/2882256

[a.alekseev]

Maybe somthing wrong with the configuration...
Could you share it?

[Boris Krajnc]

.....maybe I am a litle bit lucky :-) . I find router with  software c2951-universalk9-mz.SPA.157-3.M3. So , I upload this software to my Primary gateway and , I will wait, to see what will be in next hours. Now I run on version 15.7-3M3.

Guys, you are awesome with your support. I will report how this case will finish.

[balaji.bandi]

Seems to be Luck Favoring you now this year.. keep post us what you find for us and community.

[Boris Krajnc]

I would like to inform you, that after software upgrade everything works fine ;-)

Thank you all for your help.

Regards

[balaji.bandi]

Good to know, if the thread is helpfull and solve, mark as solve, so it will be helpfull for other community members, if they have similar issue.