I don't actually know how to define it fast and clear.
Background:
My ISP hands out broadband internet over fiber. It provides IPTV over VLAN 4 and I have no problems getting it using Zentyal. As soon as I trunk it and allow DHCP on VLAN4 I get appropriate IP address on interface.
Problems:
Problems start when I want "normal" internet as well. Internet "part" does not have defined VLAN tag. Or it's defined as VLAN 0 according to DD-WRT config files pulled from ISP official Inteno routers. ISP support technicians either don't know themselves or say I would not need any tag.
"Zentyal's GUI way" of interface configuration prohibits me from using VLAN 0 ("I'd be getting error message of appropriate values being between 1-4095). It also prohibits any other use of trunked "parent" interface although nothing in linux itself forbids it. I tried it on plain Ubuntu and got instant IP addresses on eth1 (normal Internet) and manually trunked eth1.4 (IPTV) without problems. Config file I edited was /etc/network/interfaces
I would like to see that Zentyal allow further use of trunked parent interface (possibility of assigning static IP/DHCP) and/or include VLAN0 into VLAN configuration.