Tried to make some reduced testcases: The test is done on: Linux kvm07 3.11.0-031100rc6-generic #201308181835 SMP Sun Aug 18 22:35:54 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux Later I tested it on Linux kvm07 3.11.0-031100-generic #201309021735 SMP Mon Sep 2 21:36:21 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux, the problems was not solved. eth3 - testlan driver: tg3 version: 3.132 firmware-version: 5719-v1.31 NCSI v1.1.15.0 bus-info: 0000:03:00.3 supports-statistics: yes supports-test: yes supports-eeprom-access: yes supports-register-dump: yes eth4 - vlan280 driver: be2net version: 4.6.62.0u firmware-version: 4.2.401.605 bus-info: 0000:24:00.0 supports-statistics: yes supports-test: yes supports-eeprom-access: yes supports-register-dump: no Small kvm scripts: sudo tunctl -u root -t tap42 sudo brctl addif vlan280 tap42 sudo ip link set tap42 up sudo kvm -hda vdisk.img -cdrom /srv/ganeti/iso/linux-secure-13.04-64bit.iso -m 1024 -net nic -net tap,ifname=tap42,script=no -boot d sudo tunctl -u root -t tap42 sudo brctl addif vlan280 tap42 sudo ip link set tap42 up sudo kvm -hda vdisk.img -cdrom /srv/ganeti/iso/ubuntu-rescue-remix-11-10.iso -m 1024 -net nic -net tap,ifname=tap42,script=no -boot d sudo tunctl -u root -t tap42 sudo brctl addif vlan280 tap42 sudo ip link set tap42 up sudo kvm -hda vdisk.img -cdrom /srv/ganeti/iso/clonezilla-live-2.1.1-7-amd64.iso -m 1024 -net nic -net tap,ifname=tap42,script=no -boot d Then I testet it on testlan (tg3 device), the testlan is on the same network at vlan280 All the test working sudo tunctl -u root -t tap43 sudo brctl addif testlan tap43xit sudo ip link set tap43 up sudo kvm -hda vdisk.img -cdrom /srv/ganeti/iso/linux-secure-13.04-64bit.iso -m 1024 -net nic -net tap,ifname=tap43,script=no -boot d sudo tunctl -u root -t tap43 sudo brctl addif testlan tap43 sudo ip link set tap43 up sudo kvm -hda vdisk.img -cdrom /srv/ganeti/iso/ubuntu-rescue-remix-11-10.iso -m 1024 -net nic -net tap,ifname=tap43,script=no -boot d sudo tunctl -u root -t tap43 sudo brctl addif testlan tap43 sudo ip link set tap43 up sudo kvm -hda vdisk.img -cdrom /srv/ganeti/iso/clonezilla-live-2.1.1-7-amd64.iso -m 1024 -net nic -net tap,ifname=tap43,script=no -boot d Change the two network cards, that is testlan moved to eth4, vlan280 moved to eth3 Nothing worked at vlan280 and nothing worked at testlan. We could not get at dhcp working on vlan280 (eth3 - tg3) driver. The bridge setup is as followed, with or without the mac address setup, the result is the same. And I remember to change it when change the bridge_ports. The other 10Gbit interface is used to do drbd and is working without problems. auto vlan280 iface vlan280 inet static address 10.230.80.26 netmask 255.255.255.0 gateway 10.230.80.1 dns-search fcoo.dk dns-nameservers 10.230.80.11 10.230.80.12 bridge_ports eth3 bridge_maxwait 0 bridge_fd 0 bridge_stp off post-up ip link set vlan280 address ac:16:2d:7b:35:4f # # TEST VLAN # auto eth4 iface eth4 inet manual # # TEST VLAN bridge # auto testlan iface testlan inet manual bridge_ports eth4 bridge_maxwait 0 bridge_fd 0 bridge_stp off