[mrtg] Re: Newbie questions

[Davis, Steve]

-----Original Message-----
From: mrtg-bounce at list.ee.ethz.ch [mailto:mrtg-bounce at list.ee.ethz.ch] On
Behalf Of Matthew Petach
Sent: Friday, September 24, 2004 11:13 AM
To: Ron Crummett; mrtg at list.ee.ethz.ch
Subject: [mrtg] Re: Newbie questions

--- Ron Crummett <roncrummett at mail.caynetco.com> wrote:
> Hello all -
> 
> I have been asked to monitor traffic on a remote router for one of our 
> clients, using MRTG.  I have learned the basics of setting it up but 
> when I tried running it on the router in question, I got this message:
> 
> SNMP Error:
> no response recieved
> SNMPv1_Session (remote host: "67.131.4.218" [67.131.4.218].161)
>                   community: "public"
>                  request ID: 794746515
>                 PDU bufsize: 8000 bytes
>                     timeout: 2s
>                     retries: 5
>                     backoff: 1)
>  at C:/MRTG/bin\..\lib\mrtg2\SNMP_util.pm line 627 SNMPWALK Problem 
> for 1.3.6.1.2.1.1 on public at 67.131.4.218::::::v4only at cfgmaker line 
> 827
> WARNING: Skipping public at 67.131.4.218: as no info could be retrieved
> 
> I am in a unique position where I have not studied networking until 
> now, so I am learning on the fly.  From what I have been able to find, 
> I have two
> conclusions:
> 
> -SNMP is not turned on on the router
> -the community string is wrong

Pretty reasonable guesses; there could also be an Access Control List (ACL)
blocking UDP traffic to port 161, and one should never rule out simple
issues like "is the router turned on/plugged in?"

The IP address is pingable from here, so we'll figure you have good IP
reachability to the device; so leaving the ACL possibility aside for the
moment, the next step is to check and see if SNMP is configured on the
device.

It appears to be a Cisco router; if you have the passwords to the router,
the first step is to log in and become enabled; to do so, after logging in,
if your prompt does not end with the # character, type "enable"
and then type in the enable password for the router.

Once enabled, you should be able to type "show run" 
to see the configuration on the router; you are looking for lines with
"snmp" in them.  If you are running a recent enough version of IOS, you can
speed up the process by typing "show run | include snmp"
that will show you just the lines that have "snmp" in them.

If you *don't* see any lines of the form snmp-server community BLAH then
SNMP isn't enabled on the router.  To enable snmp, type configure terminal
snmp-server community your-SECRET-community RO end write memory

This will enable SNMP with the read-only string that you replaced
"your-SECRET-community" with.

Later on, you can specify an Access Control List on the line to limit which
IPs can do SNMP queries against your device; but to start with, leave the
ACL off until you've verified you can poll the device.

For now, go back to your MRTG box, and replace "public" with the SNMP
community string you put on the router, and try doing your polling again.
With any luck, you'll find that it succeeds now.

> My problem is that I don't know what to do about either of them.  The 
> router in question is located about two hours away but I'd really 
> prefer to not drive down there for something like this, when it seems 
> to me that I should be able to do it remotely.  I just have no idea how.
> I apologize if this does not make sense, or if it is answered in the 
> documentation.  My problem right now is that as a learner, I have no 
> idea of where to start.

No need to drive.  :)

> That's it from here.  More to come as the plot thickens...
> 
> Ron Crummett
> CayNet Consulting
> (208) 424-1590 office
> (208) 850-6589 cell
> http://www.caynetco.com

Hope this helped!

Matt

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I have verified that I can ping his router from the internet, so we know
that the router is up and responding.  First, we need to verify that SNMP is
enabled and we know the correct community string.

Steve Davis
Electronic Data Systems, Inc.
Sacramento, CA

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