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ifconfig vlan_device.vlan_id create
The first thing to do is to list the VLANs that will be on the em0 adapter:
vlans_em0="101 102"
Be be to bring the parent interfaces up before you configure the IPv4 on the vlans
ifconig_em0="up"
This will cause FreeBSD to create new “virtual” network adapters called lan0.101 and lan0.102 – and these seem to function much like any other network card, you can use ifconfig on them. Then, configure the actual addresses for the new virtual adapters:
ifconfig_em0_101="inet 10.1.1.1/24" ifconfig_em0_102="inet 10.1.2.1/24"
Now reboot your system or run /etc/rc.d/netif restart - you should now see something like this in your ifconfig output:
em0.101: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500 ether 00:1b:b9:8b:ca:33 inet 10.1.1.1 netmask 0xffffff00 broadcast 10.1.1.255 inet6 fe80::210:b5ff:fe0d:9c75%lan0.101 prefixlen 64 scopeid 0x5 nd6 options=3<PERFORMNUD,ACCEPT_RTADV> media: Ethernet autoselect (100baseTX <full-duplex,flowcontrol,rxpause,txpause>) status: active vlan: 101 parent interface: lan0 em0.102: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500 ether 00:1b:b9:8b:ca:33 inet 10.1.2.1 netmask 0xffffff00 broadcast 10.1.2.255 inet6 fe80::210:b5ff:fe0d:9c75%lan0.102 prefixlen 64 scopeid 0x6 nd6 options=3<PERFORMNUD,ACCEPT_RTADV> media: Ethernet autoselect (100baseTX <full-duplex,flowcontrol,rxpause,txpause>) status: active vlan: 102 parent interface: lan0