How Troubleshooting High CPU Caused by the BGP Scanner ?

kneg · ‎05-25-2004

Hi ALL!

Our equip.: cisco 7507

We are received from ISP BGP Full view + default

and have high cpu util on 7507:

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

m10-7507#sh proc cpu his

6666666

1111111111 11111 66666 6666622

100

90

80

70 *****

60 *******

50 *******

40 *******

30 *******

20 *******

10 ***** *******

0....5....1....1....2....2....3....3....4....4....5....5....

0 5 0 5 0 5 0 5 0 5

CPU% per second (last 60 seconds)

1 1 1 1 1 1 1 1 1 1 1 1 1

6809668096908681086808680846809680974809670977099780879077

6500662028303690025807690643501750105501690907088250637043

100 * * * * * * * * * ** *** * **

90 *** ** ** * * *** *** *** *** *** ** *** *** **

80 *** *** *** * ** *** *** *** *** *** *** **** *** **

70 *************** ********** ******** *********************

60 *************** ********** ********* *********************

50 *************** ********** *******************************

40 *************** ******************************************

30 *************** ******************************************

20 *************** ******************************************

10 ###############*##########*#########*##########*##########

0....5....1....1....2....2....3....3....4....4....5....5....

0 5 0 5 0 5 0 5 0 5

CPU% per minute (last 60 minutes)

* = maximum CPU% # = average CPU%

1111111111111111111111111111111111111111111111111111111111111111111111

0000000000000000000000000000000000000000000000000000000000000000000000

100 **********************************************************************

90 **********************************************************************

80 **********************************************************************

70 **********************************************************************

60 **********************************************************************

50 **********************************************************************

40 **********************************************************************

30 **********************************************************************

20 **********************************************************************

10 ######################################################################

0....5....1....1....2....2....3....3....4....4....5....5....6....6....7.

0 5 0 5 0 5 0 5 0 5 0 5 0

CPU% per hour (last 72 hours)

* = maximum CPU% # = average CPU%

http://www.cisco.com/en/US/tech/tk365/tk80/technologies_tech_note09186a00801c4f48.shtml

says that

"High CPU due to the BGP scanner process can be expected for short durations on a router carrying a large Internet routing table. Once a minute, BGP scanner walks the BGP RIB table and performs important maintenance tasks. These tasks include checking the next-hop referenced in the router's BGP table and verifying that the next-hop devices can be reached. Thus, a large BGP table takes an equivalently large amount of time to be walked and validated."

How reduce cpu util:

1. receive default instead Full view

2. other method

Pls, help !

tbaranski · ‎05-25-2004

I'm assuming that "show process cpu" confirms that it is indeed the BGP Scanner causing high CPU usage. You may want to open a case with TAC, if possible. The BGP Scanner shouldn't consistently use so much CPU time, and troubleshooting this via a message board probably won't be easy.

bennettba · ‎05-27-2004

Couple ways to do it...

1. Increase the DRAM in your box..

2. Reduce the number of routes you're getting from your provider.. If you're only connected to one provider, there's no need to take a full table.. Take the default and watch your 7507 breathe a sigh of relief. If you're multihomed, take the default from both and set a higher local-pref to the provider with the bigger pipe. That way you'll always make it out.