High cpu and high input errors

Solutions ID:    KB4956
Version:    1.0
Status:    Published
Published date:    02/28/2012

Problem Description

Seeing a lot of input errors. Have verified cabling, switch ports, duplex settings and have replaced the ssl card (known issue on model 810 whereby the ssl card stops the intel interface card using PCI-X).



input errors on an interface can also be due to  CPU overload etc. In the case of cpu load the TCP engine in software is not able to keep up with incoming load and as a result, packets are dropped on the receive interface.
How to identify if this is a CPU/resource issue:
Under tcp interface information (https://<IP>:8082/tcp/interface), there are two useful counters below for the interface which will be non-zero. They are:
- Input errors
- Receive resource errors

Input errors
Output errors
Packets received via multicast
Packets sent via multicast
Packets received via broadcast
Packets sent via broadcast
Dropped on input
Destined for unsupported protocol
Number of receive lockups
Receive CRC errors
Receive alignment errors
Receive resource errors



If you see this then check the sizing. In this case the Wan link was 100Mbps. We were seeing about 70 Mbps of traffic. Now in this case the customer was using ADN. This was the core box in an ADN setup. It was an 810-20 which is designed for a wan link of 40Mbps in an ADN environment so was overloaded. For forward proxy i.e. no ADN then it is designed for a wan link up to 90 Mbps.

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