[LARTC] Mulitple VLANs containing the same ip subnet NATed on same box

[Grant Taylor]

Geoff Karl wrote:
> I know this is not a normal request, but I would like to connect two
> vlans into the same box that have the same subnet on them, and then
> NAT them out to the Internet.
> 
> We don't need to make any connections inbound to them, but only
> provide outbound access.
> 
> Any suggestions on how to do this?

Bridge the two VLAN interfaces together and assign your internal IP to the bridge interface.  Then you will do standard NATing between your external interface and your bridge interface.  By the way, inbound access will be just as easy as outbound.

> If I can't do it with routing then I could use something like
> user-mode Linux, or other virtualization software.

I don't think you need any thing as complicated as UML.

You could even do this with 1 network interface with everything being VLANs.

I.e.

eth0.0001	VLAN for workstations
eth0.0002	VLAN for workstations
eth0.0003	VLAN for internet access

eth0.0001 and eth0.0002 are bridge together yielding bri0

bri0		internal interface
eth0.0003	external interface

NAT between bri0 and eth0.0003.

If you ever added a second internet service provider, put them on eth0.0004 and update your routing.



Grant. . . .