Virtual Network Interfaces

['Jeremie Le Hen']

Hi Raymond,

On Tue, Oct 31, 2006 at 11:10:47AM -0500, Raymond Wagner wrote:
> Your other method is that I keep NAT on the internal interface as normal,
> and then create VLANs, bridged to the external interface, to each computer
> with an external IP.  Those machines would communicate as normal on the
> internal network, but use the VLAN interface for external access.  I've not
> used VLANs before, so I don't know exactly how they work.  I know the
> wrapper causes some overhead, and my switch drops packets >1500 bytes.  Do I
> have to lower the MTU on the internal network, or just the VLANs and
> external?  Also, will my ISP know not to send the larger packets?

802.1q (namely VLAN) adds a 4-bytes header which means your network
adapter must support a MTU of 1504 bytes.  AFAIK, most of network
cards do this.  I haven't heard of problems like this so far.

I've Cc'ed Andrew Thompson which has imported if_bridge(4) from
OpenBSD into FreeBSD.  He will likely be able to answer your question
and tell whether it is possible to bridge two VLAN interfaces
(attached to a physical interface) with another physical interface.

Regards,
-- 
Jeremie Le Hen
< jeremie at le-hen dot org >< ttz at chchile dot org >