CirrusHI,
So to me this is a question of network ranges.
So you have a external IP 25.25.25.25 and you want to have a second IP so say 25.25.25.26, now if these are just /32 address these will need to be on different interfaces on your external firewall..
Or these will need to be in same wider subnet so /24 or /27 or something like that. So one physical interface can have 2 IP's with the same gateway,
Now with that in mind, on the f5 the same will need to our if your first VIP is say 10.10.10.11, it should be in the same subnet of at least a self-ip and its gateway so should be in a /29 or higher network, which would give you a second IP say 10.10.10.12 so this address will actually be 10.10.10.12/29 to use for your second VIP make the network address wider on your external edge and you can have more VIP's / IP!. If you add a cluster you'll need an additional Self IP for each NIG-IP in that cluster.
Once you have the suitable network ranges for this to work, you then just need to map your NAT rules from external to internal and you should be ready to rock!
If you can only have one internal IP, you could always have to exteranl IP's say on port 443.
And use the external firewall to NAT them to different ports.
So something like
ExtIP01:443 => IntIP01:3001
ExtIP02:443 => IntIP01:3002
Which dependant on your constraints in your system may give you a little more flexiablity.
