Create virtual interface listening on DHCP

[Teymur]

Hi there experts.

How do I create a virtual ethernet interface on a port and make it listen to DHCP, so that when I connect that port to a router that interface gets an IP from the DHCP server of the connected device.

So like say:

Dedicating port 2 of the router for vlan9

robocfg vlan 1 ports "1 2 4 5t"
robocfg vlan 9 ports "3 5t"

Adding virtual interface

vconfig add eth0 9

Configuring the interface

ifconfig vlan9 0.0.0.0 up

WHat do I do next?

Regards

Teymur