Description

This issue will present in Highlight in the following way after clicking on the Line Health chart:

Background

• Cisco bug reference CSCty73897

  (old bug number CSCsh93041)

The issue stems from a Cisco bug which affects the ifLastChange MIB (.iso.3.6.1.2.1.2.2.1.9). This MIB value is checked every time Highlight polls the router for data and the bug causes this MIB value to creep up (it should only change if the interface has had a state change).

Knock-on effect in Highlight

The Traffic graphs show zero load.

This is due to Highlight interpreting the interface state changed between polls. Highlight therefore does not know over what time period to average the polled traffic figures so results are discarded as being unreliable.

Fix

The only fix for this is to change the IOS version (either newer or older). See the bug reference on the Cisco website for a list of IOS versions known to be affected, and also a list of IOS versions without this bug.

Identifying devices affected

Using Highlight it is usually possible to obtain a list of affected devices. Run a report by selecting Reporting and the Network tab, then:

1. Select the appropriate folder from Network Explorer tree

2. View by: a recent complete week

3. On: "Bearer Circuits"

4. Sorted By: "Availability"

5. Show Me: at least Path, Location, Name, Volume, and Availability

6. Filter on Availability Exceptions. Remove any text filter or Business Hours.

7. Results: All Results

For devices polled every 3 minutes, extract and check those with 66.6% -66.7% availability and zero bytes in and out. If required the report can be downloaded as a CSV. Find out more: reporting.

If repeated discards are displayed in the Line Health chart, possible reasons for this include:

• More traffic arrives at an interface to be sent than can be buffered there
• Traffic is being discarded as a result of a policy map applied to the interface configuration

Note that packet discards are measured as a proportion of overall packets. If more than 1 packet in 100,000 is discarded then coloured blips will be displayed, becoming red once it exceeds 1 discard every 1000 packets.

This issue will present in Highlight in the following way after clicking on the Line Health chart:

To troubleshoot non-responding devices, follow the same process as for new devices.