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Do you have any configuration tips for Cisco routers and PRTG?



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I would like to know if you have any tips on how to configure Cisco routers to monitor them with PRTG.

cisco netflow prtg sflow snmp xflow

Created on Feb 4, 2010 3:56:03 PM by  Patrick Hutter [Paessler Support] (7,225) 3 3

Last change on Jul 11, 2019 8:42:37 AM by  Maike Guba [Paessler Support]

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Accepted Answer



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This article applies to PRTG Network Monitor 19 or later

Configuration tips for Cisco routers and PRTG

This article includes several tips and tricks for your Cisco router configuration when using PRTG with SNMP or NetFlow.

SNMP-based monitoring

The following command makes sure that the router does not change the numbering of the interfaces when interfaces are added or removed so you do not have to edit your PRTG sensor setup:

snmp-server ifindex persist

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

Setting up NetFlow version 5, version 9, or IPFIX on Cisco routers for PRTG

Using the NetFlow protocol, you can monitor the bandwidth usage of all packets going through a router. For each flow of data, the router sends a NetFlow packet with connection and bandwidth information to a monitoring system that is running PRTG. In PRTG, you must create a collector that accepts these packets and does the accounting.

The advantage of using NetFlow is that it only requires little CPU load on the router itself (for example, 10,000 active flows create about 7% additional CPU load, and 45,000 active flows account for about 20% additional CPU load) and also on the machine that is running PRTG. This is much less than a Packet Sniffer sensor requires.

You must edit your router's setup and save it as the new startup configuration:

  • Log in to the router.
  • Run the command enable that gives you admin access.
  • Run the command configure.

Enabling NetFlow for each interface

The following command must be repeated for each single interface to enable NetFlow for each one (replace FastEthernet 0/1 with the names of the interfaces on your router):

interface FastEthernet 0/1
ip route-cache flow

Setting NetFlow options

See the code section below. You may want to copy the script, edit it with your IPs, and paste it into your router telnet session. When you are done and have tested the new configuration, remember to copy the new configuration to the startup configuration.

copy running-config startup-config

Disabling NetFlow

This command will tell the router not to send any NetFlow packets to the specified address:

no ip flow-export destination (address) (port)

To disable NetFlow for a specific interface, use these commands:

interface (interface) (interface number)
no ip route-cache flow

Sample NetFlow code

! Step 1: enabling NetFlow
! Note: For PRTG we need NetFlow versions 5 or 9 or IPFIX,
!       no other NetFlow version is supported currently
ip flow-export version 5
! or
! ip flow-export version 9
! Note: We recommend these values for the timeouts:
! timeout active value is in minutes
ip flow-cache timeout active 5
! timeout inactive value is in seconds
ip flow-cache timeout inactive 10 
! Step 2: setting the target address for NetFlow packets:
! Replace with the IP address of your machine running PRTG
! Replace 9991 with another port number of your choice if desired
ip flow-export destination 9991
! Step 3: you can optionally send all NetFlow packets to one other machine, too
ip flow-export destination 9991
! Step 4: create a "NetFlow Sensor" in PRTG (V7 or later) and enter the port number set above
! That's it


Created on Feb 4, 2010 3:58:52 PM by  Patrick Hutter [Paessler Support] (7,225) 3 3

Last change on Dec 4, 2020 1:14:58 PM by  Brandy Greger [Paessler Support]



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In case you need to send netflows over ipsec tunnels to the collecting probe, you might need to configure Flexible Netflows. This is described pretty well here:

If you have the condition that you see the flows get generated on the cisco device but do not reach the pingable probe machine (check by wireshark) via an ipsec tunnel, try this.

Also check the netflow version of the Cisco device. Some older firmwares seem to uses v9 by default while newer versions seem to use v5.

Created on Oct 30, 2012 4:04:38 PM by  maengling (80) 1 1



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I created a device template for Cisco Routers and, with the exception of one of the items below, all of the following items are preconfigured. I have been able to use this on all IOS devices, irrespective of their model number, which was really nice. The device template was created on Version as lacked some functionality for creating device templates. This has worked very well with auto discover using a device template.

Ping Sensor: Send multiple ping requests, ping count = 10
   Channel: Packet Loss, Enable Limits, Warning Upper = 20 (%)
All Interface Sensors: Additional channels, Errors In & Out = True; Connection state handling = Show alarnm when disconnected
   Channel: Total Traffic, Show in charts = disabled, Show in tables = disabled
   Channel: Errors In, Enable Limits, Warning Upper = 0.1
   Channel: Errors Out, Enable Limits, Warning Upper = 0.1
Uptime Sensor:
   Channel: System Uptime, Enable Limits, Warning Lower = 86400 (1 day)
System Health CPU:
   Channel: CPU 1, Enable Limits, Warning Upper = 90

EDIT: I forgot to mention that I manually edited the device template file for a couple of tweaks. Nothing that was rocket science, albeit those files get slightly scary when you really start digging throuhg them.

Created on Nov 18, 2013 6:34:18 PM by  jwalshaw (0) 2

Last change on Nov 22, 2013 12:47:45 PM by  Patrick Hutter [Paessler Support] (7,225) 3 3



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The solution mentioned from maengling saved my day. Here is the code I used Conf t flow exporter FlowExporter1 destination <PRTG Server IP> source gi0/1 transport udp 9991 export-protocol netflow-v9 output-features flow monitor FlowMonitor1 record netflow ipv4 original-input exporter FlowExporter1 cache timeout active 5 exit int gi0/0 ip flow monitor FlowMonitor1 input int gi0/1 ip flow monitor FlowMonitor1 input exit exit wr mem

Created on Sep 30, 2015 10:32:05 AM by  Aineias Matis (20) 1

Last change on Oct 9, 2015 11:28:50 AM by  Torsten Lindner [Paessler Support]



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Created on May 15, 2019 5:08:14 AM by  maestromasada (10)

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