[mrtg] Re: removing broadcast traffic

[Dowling, Steve]

Garrie,

Try using RMON and some OID maths.  You can do something like:  

InBoundPackets = TotalPackets - BroadcastPackets - MulticastPackets 

This will give you a result in packets, not bytes, but it may be better
that nothing.  

Target[InBoundPackets]:
1.3.6.1.2.1.16.1.1.1.5.<instance1>&1.3.6.1.2.1.16.1.1.1.5.<instance2>:co
mmunity at MySwitchIPAddress - 
 
1.3.6.1.2.1.16.1.1.1.6.<instance1>&1.3.6.1.2.1.16.1.1.1.6.<instance2>:co
mmunity at MySwitchIPAddress - 
 
1.3.6.1.2.1.16.1.1.1.7.<instance1>&1.3.6.1.2.1.16.1.1.1.7.<instance2>:co
mmunity at MySwitchIPAddress - 

I know it's really ugly, but I never found a better way of separating
these two types of traffic either.  

Steve Dowling



-----Original Message-----
From: Gray, Garrie [mailto:garrie.gray at eds.com] 
Sent: Thursday, 23 December 2004 2:32 PM
To: mrtg at list.ee.ethz.ch
Subject: [mrtg] removing broadcast traffic


Our implementation of mrtg is collecting wan utilisation stats from
Cisco switch ports that interface the wan routers (we do not have access
to the routers themselves). I have set the Maxbytes to be the same as
the wan links we are monitoring and it all works pretty well. Only
problem is that we are catching the lan broadcast traffic as well as the
traffic to/from the wan and this is skewing the result, particularly on
the low speed links.
 
Does anyone know of a way to weed out broadcast/multicast packets from
the utilisation graphs captured on a FastEthernet port?

If not, is there an easy way to reduce either ifInOctets or IfOutOctets
by a set amount as the broadcast traffic seems to be mostly pretty
stable? Thanks in advance, Garrie Gray Communications Service Delivery -
Canberra 
EDS Australia
Ph: (02) 6275 6881 Mob: 0408 190 184
Fax: (02) 6275 5930


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