i'm using openstack, but i think this is a more general problem. Actually i've a dedicated which comes with 1 ip address, i bought another one, and added using openstack's nova-manage cli.
So now this is what i get
$ ip addr 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000 link/ether 00:30:48:fc:4c:92 brd ff:ff:ff:ff:ff:ff inet 188.165.x.x/24 brd 18.104.22.168 scope global eth0 inet 94.23.x.x/32 scope global eth0 inet6 fe80::230:48ff:fefc:4c92/64 scope link valid_lft forever preferred_lft forever
so it seems that both ip are binded to eth0, the problems is that i don't receive packets with destination set to 94.23.x.x, when i run tcpdump -i eth0 i see packets to both ip, when i run tcpdump -p -i eth0, so not in promiscous mode, i see packets to only the first ip, so dnat and what i need won't work.
If i try to ping 94.23.x.x on the host works fine, from outside gives timeout.
$ ip route default via 188.165.x.254 dev eth0 metric 100 188.165.x.0/24 dev eth0 proto kernel scope link src 188.165.x.x 192.168.3.0/24 dev br100 proto kernel scope link src 192.168.3.1 192.168.4.32/27 dev br100 proto kernel scope link src 192.168.4.33 192.168.122.0/24 dev virbr0 proto kernel scope link src 192.168.122.1