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New Member

CPU utilization is high when traffic goes through GRE tunnel

Hi,

I have GRE tunnel configured on two 2811 router. When I try to transfer file one site to another site,  router 2811A's CPU utilization goes 86% and router 2811B's CPU utlization goes 37%. Here are the show version info;

2811A#sh ver
Cisco IOS Software, 2800 Software (C2800NM-ADVSECURITYK9-M), Version 12.4(3g), RELEASE SOFTWARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2006 by Cisco Systems, Inc.
Compiled Mon 06-Nov-06 02:36 by alnguyen

ROM: System Bootstrap, Version 12.4(13r)T, RELEASE SOFTWARE (fc1)

Cal2811 uptime is 3 days, 20 hours, 15 minutes
System returned to ROM by reload at 16:03:36 MDT Wed Oct 27 2010
System restarted at 16:04:28 MDT Wed Oct 27 2010
System image file is "flash:c2800nm-advsecurityk9-mz.124-3g.bin"

Cisco 2811 (revision 53.51) with 249856K/12288K bytes of memory.
2 FastEthernet interfaces
1 Virtual Private Network (VPN) Module
DRAM configuration is 64 bits wide with parity enabled.
239K bytes of non-volatile configuration memory.
62720K bytes of ATA CompactFlash (Read/Write)

2811B#sh ver
Cisco IOS Software, 2800 Software (C2800NM-ADVIPSERVICESK9-M), Version 12.4(9)T6, RELEASE SOFTWARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2007 by Cisco Systems, Inc.
Compiled Thu 18-Oct-07 18:01 by prod_rel_team

ROM: System Bootstrap, Version 12.4(13r)T, RELEASE SOFTWARE (fc1)

AccuLogix_Calgary_2811 uptime is 3 days, 20 hours, 17 minutes
System returned to ROM by reload at 16:00:39 MDT Wed Oct 27 2010
System restarted at 16:02:06 MDT Wed Oct 27 2010
System image file is "flash:c2800nm-advipservicesk9-mz.124-9.T6.bin"

Cisco 2811 (revision 53.51) with 249856K/12288K bytes of memory.
2 FastEthernet interfaces
2 Virtual Private Network (VPN) Modules
DRAM configuration is 64 bits wide with parity enabled.
239K bytes of non-volatile configuration memory.
62720K bytes of ATA CompactFlash (Read/Write)

Configuration register is 0x2102

2811B router has 2 VPN module and 2811A has 1 VPN module. Also I tried to upgrade the IOS image to c2800nm-advsecurityk9-mz.124-15.T13.bin which was released this year but some reason the router didn't load this image ( is this  the right image?). My question is how I can offload the CPU utilization on 2811A router and also on 2811 router what is the maximum throuput over the VPN tunnel? I will appreciate any help on this.

Thanks.

1 REPLY
New Member

Re: CPU utilization is high when traffic goes through GRE tunnel

What type of traffic flow is there.  Are you able to configure ingress

and egress flow on interface (pref. inside)

then do a "sh ip cache flow" now look at the packet size distibution.  If they are small packet then it will probably be caused by interupts

100 pkts * 50 bytes (for pktSize) will take 100 CPU cycles with t'put being 5000bytes
10 pkts * 500 bytes (for pktSize), will take 10 CPU cycles with t'put being 5000bytes As you can see, when the pkt size was 50 bytes, the CPU had to spend 10 times the work with t'put remaining the same

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