Date: Fri, 10 Jul 2015 14:04:44 +0100 From: Karl Pielorz <kpielorz_lst@tdx.co.uk> To: freebsd-net@freebsd.org Subject: lagg of em0/em1 + VLAN = lower MTU? Message-ID: <7CFE75F7566F5789DAD9FBB2@[10.12.30.106]>
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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
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