Media for C6500 High Interrupt Load caused by ARP

C6500 High Interrupt Load caused by ARP

Hello,

i have a Cisco 6509 with Sup720 running IOS (tm) s72033_rp Software (s72033_rp-IPSERVICESK9_WAN-M), Version 12.2(18)SXE4. In the last 5 days i've discovered a strange problem. The cpu load raised from 5 - 10% to

50-90% at interrupt level. The traffic hasn't changed so much. If i run a clear arp-cache the load suddenly drops down to 5 - 10% for a short time (max. 1 hour). With the growing of the arp table above 8000 entries the load raises up to 90%. What could be a reason for that? As far as i know the Cisco 6500 is able to handle more than 64k of arp entries.

c6500#sh ip arp sum

9136 IP ARP entries, with 532 of them incomplete

If i change the arp timeout to 60 seconds for example everything works fine.

All portcards are equipped with the DFC modules. The Sup720 is equipped with a PFC3B card.

Hopefully someone of you has a hint or a solution for me. Thank you in advance. If you need additional information please let me know.

Best regards,

Holger Amberg