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The interface numbers on my switch keep changing. What can I do?



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

Why is the persistence for interface numbers not working on the router?

cisco ifindex ifindex-persist interface persistance prtg router snmp snmp-compatibility switch

Created on Nov 17, 2014 4:46:08 PM by  Gerald Schoch [Paessler Support]

Last change on Jan 4, 2023 12:20:13 PM by  Brandy Greger [Paessler Support]

1 Reply

Accepted Answer



This article applies as of PRTG 22

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. So when you applied the ifindex persist command on your switch or router, did you apply it at global level or at the interface level for each interface?

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

snmp-server ifindex persist


snmp ifmib ifindex persist

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

show snmp mib ifmib ifindex


show interface snmp-ifindex

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


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 may 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.


Created on Nov 17, 2014 5:26:13 PM by  Gerald Schoch [Paessler Support]

Last change on Jun 30, 2022 7:58:30 AM by  Brandy Greger [Paessler Support]

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.