the IP that came with my Server - lets say: 1.1.1.1 ("IP-1")
and one that is routed to the same interface - lets say: 2.2.2.2 ("IP -2")

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet static
        address 1.1.1.1/22
        dns-nameservers (what my hoster set for me)
        gateway (what my hoster set for me)
        broadcast (what my hoster set for me)
        netmask   255.255.252.0

auto eth0:1
iface eth0:1 inet static
        address 2.2.2.2
        netmask 255.255.255.255

auto  br1
iface br1 inet static
  address   10.10.10.100
  netmask   255.255.255.0
  bridge_fd 0
  bridge_maxwait 0
  pre-up brctl addbr br1
  up iptables -t nat -F POSTROUTING

  up iptables -t nat -A PREROUTING -d 2.2.2.2/32 -j DNAT --to-destination 10.10.10.1

  up iptables -t nat -A POSTROUTING -s 10.10.10.0/24 -o eth0 -j MASQUERADE

  //PREROUTING (NATting)

  post-down iptables -F
  post-down iptables -t nat -F
  post-down brctl delbr br1