And if the first interface was destroyed, net that exists on another
iface, disappears from routing table:
#ifconfig vlan10 create
#ifconfig vlan10 vlan 10 vlandev rl0 up
#ifconfig vlan10 inet 192.168.156.1/24
#ifconfig vlan210 create
#ifconfig vlan210 vlan 210 vlandev rl0 up
#ifconfig vlan210 inet 192.168.156.1/24
#netstat -rn | grep 192\.168\.156
192.168.156.0/24 link#5 U 0 0 vlan10
192.168.156.1 link#5 UHS 1 0 lo0
# ifconfig vlan10 destroy
# netstat -rn | grep 192\.168\.156
192.168.156.1 link#5 UHS 0 0 lo0