excessive no of packets

[gorfan]

here is the senario:
A cisco 3745 is used for bridging and interconnecting 10 lans, forming a wan. The cpu utilization is between 10-30%. OSPF is being used for routing.
I tried to upgrade 2 of the lan routers (2620 -> 2811)
using the exact same configuration. After a minute the cpu
utilization in 3745 goes to 99%. There are more than 1500 packets/sec (usually 70 to 150) in the serial interface.

One of the lan routers was close to 3745 and when I changed the way they connect from serial to ethernet, everything goes back to normal.

Changing the ios in 2811 had no effect.
OSPF is used for routing

Multilink
fair-queue
pim
rtp compression
are enabled on the serial interface


Has anyone experienced something similar?

 

[KiscoKid]

1500 packets a sec doesn't seem a lot for a router like a 3745. You do need to determine what's causing it however (I suspect the RTP compression - esp on a very busy voip network).

Cisco have produced many documents about determing the cause of CPU issues. They tend to be due to either processes or interrupts. Read the following URL's for a list of things to check to help guide you what may be responsible:

http://www.cisco.com/en/US/products/hw/routers/ps133/products_tech_note09186a00800a70f2.shtml

http://www.cisco.com/en/US/products/hw/routers/ps359/products_tech_note09186a00801c2af3.shtml

http://www.cisco.com/en/US/products/hw/routers/ps359/products_tech_note09186a00801c2af6.shtml

http://www.cisco.com/en/US/products/hw/routers/ps359/products_tech_note09186a00801c2af0.shtml

 

[vipergg]

When the router is busy try issueing a "show proc cpu sort" and see what is driving the utilization, any compression will always add to the cpu utilization . Also make sure you have some type of fast switching turned and it is not all being process switched.