[gregoryfenton]

Figured it out (partially)

I needed to ifdown eth0:2 on my host so it freed the IP address.

Getting closer

[Myatu]

This is just a guess, since I haven't used VirtualBox in ages. But if it's setup like most other VM systems, you may need to ensure there's a route on the host so it knows to send a reply to the bridge (on which your VM is connected) rather than to the internet.

So on the host you'd have to do something like (which you can add to your /etc/network/interfaces stanza once you know that's the issue)

route add 94.23.158.94 dev br0

Where "br0" is the actual bridge device created by/for VM.

[gregoryfenton]

Short version:
I have set up my dedi with virtualbox headless.
I have created a MAC address for my failover IP.
Here is my /etc/network/interfaces inside a VM:

auto lo
iface lo inet loopback

iface eth0 inet static
	address 94.23.158.94
	netmask 255.255.255.255
	#network 94.23.158.94
	broadcast 94.23.158.94
	post-up route add 94.23.158.254 dev eth0
	post-up route add 91.121.5.142 dev eth0
	post-up route add default gw 94.23.158.254
	post-down route del 94.23.158.254 dev eth0
	post-down route del 91.121.5.142 dev eth0
	post-down route del default gw 94.23.158.254

My issue:
I can ping, traceroute, wget etc any site apart from on my actual server from inside the VM.
If I try to ping my server I get 100% packet loss.
If I try to wget a file on my server I get timed out.
If I try to traceroute my server I get the first hop (91.121.5.253) and then no further.

If I try the same with a different server (even one directly next to my server) I have no problems at all and traceroute shows the hops.

Any ideas, questions you need answering or a complete solution would be massively appreciated