On Fri, Mar 12, 2010 at 3:20 PM, Arun Khan <[email protected]> wrote:
> There is *no* client side ISP router - just a modem for media conversion

Without a client side router, you can't setup any VLANs.  Any VLAN
config needs to be done at the ISP end as your modem is just an L2 bridge.

Btw, which ISP are you using here?


> This would imply a switch supporting VLAN right?  If yes, the client
> does *not* have the infra.

A switch is not essential, you can use VLAN trunks between your
device and the local router.  But as mentioned, you cannot run VLAN
trunks to a modem, so VLANs do not apply to you and this discussion
is just academic interest.


> The appliance is an Intel Atom DG945GCLF based nettop with 2 NICs (one
> for LAN and one for WAN)
> Would appreciate some pointers If you are suggesting to do VLAN in
> Linux on the WAN NIC.

See vconfig/ifconfig man pages.  There's plenty of docs online, here's one:
http://nixcraft.com/networking-firewalls-security/10447-linux-vlan-configuration.html

Not all NICs support VLAN interfaces, the VLAN tags add 4 bytes to the ethernet
frame so the NIC must support 1512 bytes MTU.  I have the same Intel Atom board
at home and it runs tagged VLANs without any issues, so you'll have no problems.


> This possibility also exists in VLANs does it not?  In my scenario, at
> the L2 layer, it is a point to point connection with the service
> provider (who is providing both MPLS VPN as well as Internet)

You're probably right.  In most of my setups, I use 2 different ISPs
when are terminated on a single router, and VLAN trunks created to
the firewall.  The firewall has total control over packets passing between
the ISP and internal interfaces.

- Raja
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