How to pass VLAN trunk to VM in Hyper-V 2008 R2

As long as you tag VM NIC with proper VLAN ID under VM settings \ networking in hyper-v console, your VM can talk to external network with trunk port
No special configuration is required for that.
You need to ensure that trunk port is correctly configured from network end

Ok, how do you get 20 VLANs to the VM? Maybe Im missing something...

Not sure if understand your query

All you need to do is create trunk (merge) on physical switch port for all those 20 VLANS so that switch port will pass tarffic between those VLANS.
Now assign required VLAN out of 20 to VM network in hyper-v VM settings and that VM should talk to any VLAN out of 20

You mean I can use one of 20 VLANs with one VM. My question is to use 20 VLANs with one VM. VM is VLAN aware, it is router, which can route among them, now it is physical, i need to transform it to virtual.

U can,t assign multiple VLANs to either VM or physical server.

When you do trunk, you need to tag perticular VALN ID to VM so that it can tell trunk port that I have traffic from perticular VLAN segment and trunk port will then pass tarffic to appropriate VLANs

Physical machine can handle it... Kerio Control, Mikrotik and others can handle VLAN trunk connected directly to NIC