Add the following to /etc/network/interfaces replacing index and the IPv4 address with the address of your virtual server:
auto lo:index iface lo:index inet static address IPv4-address netmask 255.255.255.255
For example: If your virtual server was 10.1.1.8 and you decided to use index 0, you need to add the following:
auto lo:0 iface lo:0 inet static address 10.1.1.8 netmask 255.255.255.255
Make sure to specify the netmask 255.255.255.255 (and nothing else). The index may be any number starting with 0.
Add the following to /etc/network/interfaces replacing the IPv6 address with the address of your virtual server:
iface lo inet6 static address IPv6-address netmask 128
For example: If your virtual server was 2001:db8::2:4 you just need to add the following:
iface lo inet6 static address 2001:db8::2:4 netmask 128
For IPv6 it’s important to specify netmask 128, this makes that the specified address has no network part (covering all 128 bits).
Just add the following two lines at the end of /etc/sysctl.conf:
sometimes /etc/sysctl.conf gets overwritten during an update, so in case of ARP problems check if this entry is present on all targets.