VLAN 0 and pfSense

  • I've been giving a bit of thought to VLAN 0 today. As I understand it, the purpose of VLAN 0 is to provide priority support to native LAN frames. If I understand this correctly, that means the only difference between VLAN 0 frames and others is the VLAN tag, with things like IP subnet, gateway addresses etc., the same as other frames. Is this sort of thing supported in pfSense, in that it will accept VLAN 0 frames for things like DHCP requests, IP forwarding, etc.? If so, I assume I'd have to configure the VLAN 0 interface exactly the same as the native LAN interface.

    Has anyone tried something like this?

  • Yes, you are correct, conceptually, VLAN 0 basically does allow the priority bits to be transmitted on native VLAN frames, but the device that is receiving the frame has to understand this and deal with it. It appears to me to be a "hack" to allow some specific type of networking gear found in process and power system automation to support priority, and probably predates DSCP.
    I have no clue as to whether or not the NIC drivers will handle this, nor how it will pass the packets up the stack. I suggest you dig around in FreeBSD forums for that.
    In the interim if you're only looking for the priority part, DSCP is a much better alternative, as it is supported on both tagged and untagged frames, and pretty much all modern networking equipment supports it.

  • @awebster

    I am aware of diffserv and and even used it. However, since that's layer 3, it would have no effect at layer 2. So, it could be used for priority through routers, but it wouldn't do anything at the Ethernet level. One of the reasons for using a VLAN for VoIP is to give it priority over other data.

    However, this is more wondering about it, rather than having a need at the moment.


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