VLAN MTU problem in 4.9 ?

["." at babolo.ru]

> Setting the MTU to 1496 on the router vlan interfaces didn't seem to help 
> me... however put the MTU to 1496 on the servers on the VLAN itself seems to 
> resolve the problem.  so in the current configuration the router vlan 
> interfaces are set to 1500 and the servers on those interfaces are set to 
> 1496.  Seems to work for now.
> 
> Now, this doesn't seem all that normal.  Where can I go from here to 
> troubleshoot this more and provide more information that might be able to 
> resolve this problem... if it's a problem that is...
You can't be free from tune all your net for vlan mtu:
 - all switches involved must be at least verifyed not to drop long frames
   or right route vlans if it can work with tag based vlans
 - all interfaces in selected vlan must support the same common mtu

I know now, that xl interface can't pass 1504 frames
and most 1G interfaces can
 don't know about another 100M interfaces