SNMP management software

[cox]

I have a number of wan links that I monitor the utilisation of. I use network instruments observer software to do this, however, I have noticed that on numerous occassions the interface % utilisation will go well over 100%, I have checked that the interface index in the MIB is correct and that Observer recognises the correct speed of the interface. Do I need to add any commands to the router in order for the software to interpret the data correctly ?

Thanks

[drussell]

Usually this is due to processing delays.

Utilizaion is calculated by (delta ifInOctets)/(delta time). We can be pretty sure about the octet counts but not about the time values. The delta time might be fixed to be the program's sampling times. However, the data is based on when the request was received by the device.

if there was some delay in actually transmitting the request or in getting the second IfInOctets value back from the device the real delta time is longer than the one used in the calculation, the result of the calculation will be >100%.

The next value is probably lower than it should be since the next actual delta time is probably smaller than the one used.

Another source of error will be the frequency that the device updates its SNMP counters. The value might be 200ms old of 1 ms old.

[cox]

Thanks for the info, is there anything that can be done to resolve this?

[drussell]

I am not familiar with the program you are using. Some common places to look are:

1. Check the CPU load on the machine running the program

2. Make sure that the host machine has enough memory so that swapping to disk is not an issue.

3. Check to see if the application is able to schedule enough SNMP requests to keep them from queueing up.

4. Make sure that the the DNS database has all the names and addresses.

5. Verify that the WAN device is returning data accurately and promptly.

The vendor may have more specific solutions since this is not an unusual problem.

[cox]

Many thanks