vlan double tagging

[Wilkinson, Alex]

     0n Sat, Dec 18, 2004 at 03:16:27AM -0500, James wrote: 
     
     > On Fri, Dec 17, 2004 at 03:03:49PM -0800, Mike Hunter wrote:
     > > On Dec 17, "Brooks Davis" wrote:
     > > 
     > > > On Fri, Dec 17, 2004 at 01:22:02PM +0200, Donatas wrote:
     > > > > hello,
     > > > > i'd like to ask if there's any possibility to pass double tagged vlan packets through freebsd 5.x routers?
     > > > > and....how many level1 vlans are supported on one parent device?
     > > > 
     > > > I don't know what happens with double tagged vlan packets.
     > > 
     > > I think what he's asking about is whether FreeBSD prevents any of the
     > > nasty hacks that can be accomplished by double-tagging frames, or if there
     > > is something he can do with netgraph to prevent such badness.
     > 
     > /me thinks he's asking for q-in-q tunneling feature.

What is 'q-in-q tunneling' ?

 - aW