How do I configure two IP addresses on a specific vlan

Solution 1:

I don't know when and what changed, but you can now define virtual interfaces on vlans:

auto eth0.10
iface eth0.10 inet static
    address 192.168.1.61
    netmask 255.255.255.0
    gateway 192.168.1.11

auto eth0.10:1
iface eth0.10:1 inet static
    address 10.20.100.100
    netmask 255.255.255.0

auto eth0.10:2
iface eth0.10:2 inet static
    address 10.20.100.200
    netmask 255.255.255.0

Think of vlan interfaces as physical interfaces. You add virtual interfaces to the "physical" interface.

Solution 2:

It looks like this is actually not supported. What you can do is add several up or post-up stanzas which can then add addresses to an interface. I opted for this solution:

auto eth0.10
iface eth0.10 inet static
    address 192.168.1.61
    netmask 255.255.255.0
    post-up ip address add 192.168.1.62 dev $IFACE