This article applies to Network Monitor 12 or later, as well as to previous (deprecated) versions

Enabling 32-Bit Counters for Cisco Routers

For some reason, sometimes Cisco routers do not show certain interfaces unless you force 32-bit counters. To do so, please follow these steps:

1. In the PRTG web interface, choose your Cisco device from the device tree.
2. Select the Settings tab.
3. Scroll down until you see the SNMP Compatibility Options entry.
4. Uncheck inherit from .... You can now change the compatibility options.
5. In section 32-bit/64-bit Counters, select the option Use 32-bit counters only (see screenshot below).
6. Click on Save.
7. Add the sensor anew.
8. Adding the counters should now work.
9. Please remember to turn off the 32-bit option (i.e., choose Use 64-bit counters if available) after adding the sensor.

Note: If a lot of traffic is going through your the 32-bit interface, please make sure you select a small scanning interval to prevent a 32-bit overflow in your device. An overflow would cause your device to overwrite its own monitoring data before it is sent to PRTG and therefore lead to incorrect data. A 32bit counter can store a maximum of 2^32 bytes.

SNMP Compatibility Options of PRTG