[OpenWrt-Devel] vnstatd and collectd inconsistency with vlan interfaces

Daniel Dickinson openwrt at daniel.thecshore.com
Mon Feb 15 04:07:31 EST 2016

I discovered the issue is not with vlans but with the way I was routing 
traffic from openwrt as a virtual router for virtual machines running on 
the same laptop, for which I want routing out the appropriate vlan for 
type of host (e.g. home vs. work) when connected to the local network, 
and a combination of internet traffic out the natted wan when working 
remote, and traffic destined for my base (remote from the point of the 
view of the travelling laptop) to route via vpn for the appropriate vpn 
connection for the appropriate vlan.

I had not gotten the routing right and was routing all traffic out the 
wan of the virtual router instead of routing each vlan's traffic out the 
appropriate vlan on the virtual router (takes using routing rules and 

Hence what I eventually noticed is that the wrong interface on the main 
router was getting all the rx traffic I was expecting on differentiated 



On 14/02/16 01:44 AM, Daniel Dickinson wrote:
> Hi all,
> I discovered through that despite over 23 GB of upload in past 24 hours
> that neither vnstat nor collectd are reporting even close to that amount
> traffic on the lan side.
> I didn't have wan reporting statistics on vnstat, so that side of things
> is missing, but the lan traffic for the raw vlan interface is rx 1.67
> GIB and tx 5.14 GiB, and the bridge it's part of reports rx 2.05 Gib and
> tx 5.21 GiB.
> Collectd on eth1 (wan) reports correct traffic, but raw vlan and bridge
> interfaces on the lan side are about the same as vnstat.
> What exactly are they measuring that the lan side of the equation
> reports such different results from the wan?
> I would expect to see approximately balanced rx on the lan and tx on the
> wan, but that is not the case, and the lan traffic is consistent for
> vnstat and collectd and I thought they used different methods of
> collecting the data, which means that there is common reason for the
> behaviour.
> Is there something about vlans that affects the way traffic gets
> accounted for in the linux kernel?
> Regards,
> Daniel
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