[mrtg] Re: Pulling port information using MRTG

[PAUL WILLIAMSON]

By default, MRTG grabs the ifInOctets and ifOutOctets 
of every interface it can see.  On Cisco devices, 
this is somewhat determined by the OS level.  When 
you run cfgmaker against a device, it determines 
what interfaces or up or down administratively, and 
comments the down ones out.  The interfaces are 
generally "indexed" which is how MRTG assigns the 
number to them.  The target name is the interface 
index unless you have added the command "ifref=option" 
to your cfgmaker at runtime.  The the target (and 
resulting data file) will be called that way.  I 
have targets that are referenced all kinds of ways - 
by DNS name, by ip address, and some even by function. 

The .my files Cisco has on their website are MIBs 
specific to either a device, and OS revision, or both.
I have no idea why they end in .my.  Within those 
MIBs are the specific OIDs for associated devices 
you can look at.  

The 1:target or 2:target is just shorthand for MRTG 
to grab ifInOctets&ifOutOctets on that index.  If 
you want to graph your own custom OIDs, you need to 
put them into the file in exactly that format 
(OID1&OID2) - MRTG always expects 2 OIDs.  You can 
also do math on them, but this is the basic format.

HTH!

Paul

>>> "Monache, Chris" <CMonache at Empirix.com> 04/25/02 05:20 AM >>>

Hello,

How are you? I have been using the MRTG information for a few days to
monitor the following three switches:

	?EExtreme Summit24
	?ECatalyst2924
      ?ECatalyst3550-12T

I would like to know how MRTG is able to collect the traffice level for the
individual ports 
for these switches. I would like to use SNMPWALK to check some of the
values. Is
specific Port information my nd OID value? Actually more than verification
I would like to 
understand more about how MRTG is collecting data and OID information in
general.

I have been trying to find this information online but have not been able
 to.

Could you help me out or point me in the right direction?

Thanks!

Chris


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