High CPU usage due to BGP router process

[Salja]

Hi all,

I have a problem with higher CPU and memory usage because of BGP router process on the Cisco 6500.

I have 2 routers, ASR 9001 and Cisco 6500 with SUP 720-3bxl. Each router has one eBGP connection to the ISP with full BGP table.

There is also iBGP session between the routers and right now I am advertizing around 11000 prefixes from ASR to 6500.

These 11000 prefixes are from direct peering to the local IX. As soon as I shutdown iBGP session or session to the direct peering everything is normal again.

I've also checked for possible route "churn" from direct peering neighbor and I was not able to find any frequent changes of the best path for any prefix.

On the 6500 is still available around 170MB of memory (1G in total). Before I had on the same device 2 full BGP tables and around 20 direct peering session and everything was working normally with avarage CPU usage a bit below 20%.

Right now the CPU avarage usage is around 30% and BGP router process is above 10%:

 447  1309762744 332909565       3934 12.00% 12.14% 13.34%   0 BGP Router   

Any advice would be appreciated!

Thank you

Salja

[Hitesh Vinzoda]

Dude,

Try this

Use these procedures in order to troubleshoot high CPU due to BGP scanner or BGP router:

• Gather information on your BGP topology. Determine the number of BGP peers and the number of routes being advertised by each peer. Is the duration of the high CPU condition reasonable based on your environment?

• Determine when the high CPU happens. Does it coincide with a regularly scheduled walk of the BGP table?

• Execute the show ip bgp flap-statistics command. Did the high CPU follow an interface flap?

• Ping through the router and then ping from the router. ICMP echoes are handled as a low priority process. The documentUnderstanding the Ping and Traceroute Commands explains this in more detail. Ensure regular forwarding is not affected.

• Ensure that packets can follow a fast forwarding path by checking whether fast switching and/or CEF are enabled on the inbound and the outbound interfaces. Ensure that you do not see the no ip route-cache cef command on the interface or the no ip cef command on the global configuration. In order to enable CEF in global configuration mode, use the ip cefcommand.

• Obtain output from these commands:

  Command	Description
  Show mls cef summary	Displays the number of routes in the Multilayer Switching (MLS) hardware Layer 3 switching table for all the protocols.
  show mls cef maximum-routes	Displays the current maximum route system configuration.
  show mls cef exception <status>	Displays information about the Cisco Express Forwarding exception status.

• Verify the DRAM on the router. As per the recommendation, there should be a minimum of 512 MB of DRAM space per BGP peer that sends the full Internet routing table. If the router has two EBGP peers that run the full Internet routing table, then a minimum 1 GB of DRAM space is recommended. The DRAM space mentioned.

Cheers

Hitesh