Setting up SNMP with PRTG Traffic Grapher

[Pistol]

IM struggling with setting SNMP monitoring up within PRTG (a great free tool for monitoring network uptime and bandwidth). Wonder if anyone can help please? Ive read the instructions but still not connecting..

in my router setup i think i need to allow port 161 for snmp, but i have set that up in my port forwarding section and still no go. In previous routers i had the choice of what port to use, i dont seem to here. default is 161 i believe though. Here are the only options i have for snmp in my router:

SNMP Settings

SNMP Agent :      i have this ticked
Read Community :      public
Set Community :              private
System Name :      dont need i think
System Location :    dont need i think 
System Contact :    dont need i think 
Trap Manager IP :    i have to enter something here, so put a local ip addy but again i dont think i need this

Its not my windows firewall as it wont work even with it off.

in PRTG when i try and find the snmp connection it says

Sorry, the scan for available monitoring items has failed!

Error Message: "No response (check: firewalls, routing, snmp settings of device, IPs, SNMP version, community, passwords etc) (SNMP Error #-2003)

For SNMP Sensors

PRTG reads the traffic data and other values from your routers/devices using SNMP (Simple Network Management Protocoll) which must be installed and enabled on your device. Please go through the following checklist:

    * Is SNMP installed and enabled on the device? (see configuration of the device)
    * Are you using the correct IP, Port, Community String and SNMP Version?
    * Does your machine running PRTG have access to SNMP? (see device's security settings)
    * Double check the "SNMP Community String" and/or passwords (these values are case sensitive) and also the SNMP Version

All parameters mentioned above will show a connection failed message if set incorrectly!

Firewall issues: If the device and the monitoring machine are on two different sides of a firewall make sure that UDP access to port 161 (SNMP) is allowed and you will also need the return path open. SNMP uses UDP not TCP, so SNMP requires the use of UDP ports >1023 to the PRTG client side so that the results can be sent back from the device to the machine running PRTG.   

Anyone point out what is probably obvious to me please so i can get this to work? cheers

[Rik]

You lost me just after PRTG, but I suppose the most obvious question would be does the router support SNMP correctly?

[Pistol]

*chuckles*
Well it says this:

SNMP Setup
SNMP is a popular management protocol defined by the Internet community for TCP/IP networks. It is a communication protocol for collecting information from devices on the network.

Read community
    This is the SNMP community name/password to read SNMP values.
Set community
    The SNMP community name/password to set SNMP values.
System name
    Optional SNMP system name.
System location
    Optional SNMP location.
System contact
    Optional SNMP system contact.
Trap manager IP
    IP address of SNMP hosting trap manager, where SNMP messages will be sent.

Which leads me to think it does...

[Rik]

I did say correctly.

[Pistol]

  touche.. my router and me are not best of buddies atm.. ok im now going to fight with Vista...

hmm, it seems Vista by default does not enable snmp. I have now done so and started the services, but it doesnt make a difference.

hmm, maybe ye can help explain this to me in plain words..

"if the device and the monitoring machine are on two different sides of a firewall make sure that UDP access to port 161 (SNMP) is allowed and you will also need the return path open. SNMP uses UDP not TCP, so SNMP requires the use of udp ports >1023 to the PRTG client side so the results can be sent back from the device to the machine running PRTG."

I have setup 161 port forwarding to my local ip.
i tried adding a rule for 1023 for udp to my local ip, but it actually replaces the 161 rule.... wtf?

what does the 2nd part mean i have to do? hmm ta!

[Rik]

If I read that correctly (highly unlikely) you need all UDP ports from 1023 upwards open, not just one.

[Pistol]

Thats what i was thinking... seems a little much.. hmm ill try that and see, ta