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Monitoring my Cisco switch doesn’t work properly with SNMP. What can I do?

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I try to monitor traffic for several interfaces on my Cisco 3560 switch via SNMP. The speeds are charted incorrectly; the bandwidths are much higher than shown in PRTG. What can I do?

cef cisco cisco-express-forwarding netflow prtg snmp

Created on Feb 5, 2013 1:41:17 PM by  Gerald Schoch [Paessler Support]



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This article applies to PRTG Network Monitor 12 or later

Monitoring Cisco Devices Which Use CEF

Cisco uses a technology called Cisco Express Forwarding (CEF). CEF is a Cisco proprietary protocol. This technology increases packet switching speed. For more details, see Cisco Express Forwarding Overview.

If CEF is enabled, PRTG does not see the packets which are transmitted when monitoring via SNMP. It is possible to disable CEF to resolve this issue, but this will affect the performance of the Cisco switch (see Enable and Disable CEF or dCEF).

If you do not want to disable CEF for performance reasons, we recommend using NetFlow (if supported by the specific device) instead to monitor the bandwidth of your Cisco switch (see PRTG Manual: Monitoring Bandwidth via Flows).

Created on Feb 5, 2013 1:42:05 PM by  Gerald Schoch [Paessler Support]



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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.