[c-nsp] How to pass VLAN through router

[Pavel Dimow]

Is this possible at all? I ended in pretty ugly scenario (for a short
time period I hope) where I must pass VLAN through router (yes router
not L3 switch). The scenario is:

 SW1-----trunk-----R1-----trunk-----R2-----trunk-----L3SWITCH

I don't have control over SW1 and R1, but I do know that I have trunk
from my R2 to other side R1 for sure (I already terminate one VLAN on
R2). Now, I need somehow to get VLAN from other side (SW1) to L3SWITCH
where I will setup a SVI.

Any thoughts? How router behaves considering VLANs? Is it only
possible to terminate vlan on subinterface and no vlan passing? It is
logical to me, because router is a router not a switch (in my case R2
is Cisco ASR). And IF router will pass VLAN over trunk interfaces how
do I control which VLANs are allowed to pass over which interface?