Help connecting to two networks (Adding a virtual interface)

Ben Scott dragonhawk at gmail.com
Tue Sep 1 17:49:50 EDT 2009


On Tue, Sep 1, 2009 at 3:45 PM, Bill McGonigle<bill at bfccomputing.com> wrote:
> IIRC, many wireless AP's don't support 802.1q in 802.11.

  Why would the AP care?  VLAN frames are just regular Ethernet
frames, but with a particular frame type that VLAN-aware nodes
recognize as the VLAN tag.  Equipment that isn't VLAN-aware should
just see it as an unknown frame type.  VLANs even eat up a few bytes
of the regular Ethernet MTU.

  (Note that I'm not arguing against the possibility or actuality.
I've learned that tech mfgs could screw up a one-man parade in a ghost
town.  But I'm still curious as to why/how.)

> Then there's hardware/driver support ...

  If we're talking strictly Linux, VLANs are implemented in the
generic link-layer, above the NIC drivers.  It's not like 'doze where
the NIC drivers are actually responsible for VLAN implementation.

> You'd at least have to tag the WAP's ethernet port
> with both VLAN's ...

  You could also run one VLAN tagged and the other untagged, if you
have existing stuff you don't want to mess with, but that stuff only
needs one VLAN.  For example, Windows clients.

> Even with 802.1q in 802.11 support I don't think you'll get any QoS on
> the wireless side ...

  Probably not with the typical SOHO stuff, i.e., LinkSys, NetGear,
etc.  I've heard of (but not looked into) "enterprise grade" WAPs
which can do QoS for VoIP applications.  I have no idea how well they
work myself, although I've heard others -- who weren't selling them,
AFAIK -- recommend them for the purpose.  YMMV, etc.

-- Ben


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