503: Service Unavailable

First, we need install vlan package to get available the 8021q kernel module:

host01# apt-cache show vlan
host01# apt-get install vlan
host01# echo 8021q >> /etc/modules
host01# modprobe 8021q

Finally, we can edit your network configuration as following:

host01# cat /etc/network/interfaces 
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).
# The loopback network interface

auto lo
iface lo inet loopback

# The primary network interface
allow-hotplug eth0
iface eth0 inet dhcp

auto eth0.206
iface eth0.206 inet static
address 10.6.60.165
netmask 255.255.255.0