[mrtg] Re: How to measure VLAN Traffic with MRTG ?

Eric Brander eric_mailing_list at rednarb.com
Tue Sep 6 15:36:51 MEST 2005

nobody wrote:

>My Question:
>Does a Switch store some VLAN Information like Traffic/Bandwidth etc in 
>a special part of the MIB? If so, i could directly read out these values 
>and display it without having problems when the configuration of the 
>Switch changes.
>(I know that the Cisco Switches produces an "interface - entry" for 
>every VLAN, but i did not find something about the Traffic)
When I run cfgmaker on my 4006 with Sup3 (for layer-3 switching) it also 
gives me each vlan as an interface.  Its a little misleading however, 
since that only reports information that traverses the vlan border, not 
that which stays within the vlan. So if traffic goes from machine A on 
vlan1 to machine B on vlan1, nothing will be seen of this traffic on the 
vlan graph. But if machine B talks to machine C on vlan2, you'll see 
that traffic on both vlan1's and vlan2's graphs.

As for aggregating the total traffic within an entire vlan, I've found 
no way other than adding interfaces together.

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