acquire vlanid via dhcp

[Pilsner]

Hello to all.
I recently changed my ISP and noticed that cannot connect to the internet, actually even ping the default gateway failed. Connection is set up in pretty standard way: ethenet cable + IP config via dhcp. What annoyed me even more, internet connection was fine under Wnidows.
I captured traffic with WireShark and noticed that ARP-replies are tagged with 802.1q vlan, say vlan-id 1234.

I know that there is vconfig, but not sure if I can make it possible to acquire all relevant info from DHCP server to have my vlan-ID configured on eth0 interface. What is the right way to make this config in Gentoo: to have vlan configured and IP address acquired via dhcp?