I'm collecting netflow data from my Airport Express. I have an OpenBSD machine acting as the router for my AIRPORT VLAN (one of very many VLANs) and use the following in pf.conf
(it collects pflow data for all passed packets):
set state-defaults pflow # AIRPORT is the "descr" for the associated VLAN interface pass in on AIRPORT all label "AIRPORT in" pass out on AIRPORT all label "AIRPORT out"
Send the collected pflow data to your netflow server on port 12345 on host 10.100.5.2:
# cat hostname.pflow0 flowsrc 10.100.5.1 flowdst 10.100.5.2:12345
Just setup a small little OpenBSD machine to handle your internal network routing and that's all there is to it. If you setup a VLAN trunk on an OpenBSD physical interface and tag all associated VLANs on the connected switch port then you're good to go.