Actually a crossover cable can be used.
Gigabit introduced Auto MDI-X
, it automatically detects the cable type (crossover/straight).
So with gigabit, it simply doesn't matter.
But I'm curious what happens if a gigabit interface is connected to lower speed one.
Does the gigabit interface still do Auto MDI-X?
//edit
Most 100 Mbit/s device should support Auto MDI-X too.
In the openwrt wiki there is only one ISP listened that uses fiber and vlan id 34 and that is:
Bell Canada Fiber, is that your ISP?
//edit
There are two: Telfort also uses 34.
The VLAN tagging is usually as follows:
Phone: VLAN 34
Internet: PPPoE over VLAN 35
TV: VLAN 36
If Bell Canada Fiber is your ISP you can try VLAN (id) 35 instead of 34.
//edit2
Also both use pppoe instead of DHCP, so scratch that.