lagg of em0/em1 + VLAN = lower MTU?

[Karl Pielorz]

Hi,

I've got a 10.1 box with a couple of Intel(R) PRO/1000 (82571EB) cards in 
it, e.g.

"
em0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
options=4019b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,TSO4,VLAN_HWTSO>
...
"

I've set these up as a fail-over lagg interface, lagg0:

"
lagg0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
options=4019b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,TSO4,VLAN_HWTSO>
...
 inet y.y.y.y
...
 laggproto failover lagghash l2,l3,l4
 laggport: em1 flags=0<>
 laggport: em0 flags=5<MASTER,ACTIVE>
"

This works fine. If I add a VLAN now to that, I end up with:

"
lagg0.10: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 
1496
...
inet x.x.x.x
...
        vlan: 60 parent interface: lagg0
"


The MTU on lagg0.10 has shrunk by 4 (size of VLAN tag). Is there a way of 
avoiding that?


-Karl