This article applies as of PRTG 22


I have enabled ifindex persist on my switch, but the interface numbers still keep changing. I fixed monitoring using the SNMP Compatibility Options with the Port Identification setting, I prefer configuring it directly on the switch. 

Why isn't interface number persistence working on the router?

Setting ifindex persist directly on the device

You can set "persistence" for interface numbers globally or at interface level. The global command does not override local settings, so you may need to modify the interface-level settings.


Depending on the IOS (Internetwork Operating System) version of your device, the command to globally enable persistence is:

snmp-server ifindex persist

or

snmp ifmib ifindex persist


To determine your current settings, run the following command on your router or switch:

show snmp mib ifmib ifindex

or

show interface snmp-ifindex

If necessary, change the settings of specific interfaces with the ifindex persist command.


Debugging

To debug issues with persistence, run the following command on your switch:

dir nvram:ifIndex-table


This command will give you a result that looks like this:

Router # dir nvram:ifIndex-table
Directory of nvram:/ifIndex-table

    2  -rw-           0         <no date>  ifIndex-table

126968 bytes total (114116 bytes free)

If you see a zero in the middle of the output, you might have forgotten to run copy running starting. If so, copy the running config into the startup config and run the dir nvram:ifIndex-table command again.


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Disclaimer:
The information in the Paessler Knowledge Base comes without warranty of any kind. Use at your own risk. Before applying any instructions, please exercise proper system administrator housekeeping. You must make sure that a proper backup of all your data is available.