Configuring VLANs - Why is IP address require on NIC connected to Trunk?

Steve Polyack korvus at
Thu Jun 18 14:17:13 UTC 2009

Geoff Roberts wrote:
> I find I have to give the ext0 interface an IP address in order for routing 
> and packet filtering to work on the attached VLANs.

This shouldn't be the case.  The "ext0" interface should not need an IP 
address for the two vlanX interfaces to function correctly.  Are you 
sure you're setting the vlandev on the child interfaces?  Perhaps you 
need to force the ext0 interface "up".  If em0 is your external/trunk 
interface, you should have something like:
cloned_interfaces="vlan0 vlan1"
ifconfig_vlan0 ="inet X.X.X.X netmask X.X.X.X vlan 0 vlandev em0 up"
ifconfig_vlan1 ="inet X.X.X.X netmask X.X.X.X vlan 1 vlandev em0 up"

After that, you should be able to simply filter on the vlan0 and vlan1 
interfaces using pf.

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