$ ifconfig udav0
udav0: flags=8843 mtu 1500
        lladdr 00:0a:79:64:b4:09
        media: Ethernet autoselect (100baseTX full-duplex)
        status: active
        inet 192.168.0.10 netmask 0xffffff00 broadcast 192.168.0.255
        inet6 fe80::20a:79ff:fe64:b409%udav0 prefixlen 64 scopeid 0x5
        inet 192.168.0.11 netmask 0xffffffff broadcast 192.168.0.11
        inet 192.168.0.12 netmask 0xffffffff broadcast 192.168.0.12

ifconfig / ifconfig -a is different, no aliases:
lo0: flags=8049 mtu 33208
        groups: lo
        inet 127.0.0.1 netmask 0xff000000
        inet6 ::1 prefixlen 128
        inet6 fe80::1%lo0 prefixlen 64 scopeid 0x4
em0: flags=8843 mtu 1500
        lladdr 00:0a:e4:3b:19:09
        groups: egress
        media: Ethernet autoselect (100baseTX full-duplex)
        status: active
        inet6 fe80::20a:e4ff:fe3b:1909%em0 prefixlen 64 scopeid 0x1
        inet 10.159.165.153 netmask 0xfffffe00 broadcast 10.159.165.255
ath0: flags=8822 mtu 1500
        lladdr 00:14:a4:44:cf:8f
        groups: wlan
        media: IEEE802.11 autoselect
        status: no network
        ieee80211: nwid ""
enc0: flags=0<> mtu 1536
udav0: flags=8843 mtu 1500
        lladdr 00:0a:79:64:b4:09
        media: Ethernet autoselect (100baseTX full-duplex)
        status: active
        inet 192.168.0.10 netmask 0xffffff00 broadcast 192.168.0.255
        inet6 fe80::20a:79ff:fe64:b409%udav0 prefixlen 64 scopeid 0x5