For the 2014 range of servers they allow a total of 64 slots. This means you can have a total 64 different types of IP routed to an server. Typically IP are thought of individually and each IP would be considered as a slot. If we used one single IP per slot, this would mean we would have 64 IPs over 64 slots.

Slot 1
Slot 2
Slot 3
Slot 4
Slot 5

Based on this method, the server will go up to slot 64 and only have 64 IP. This means if we wanted our 65th IP, this wouldn’t be possible as all slots has been filled up.

Instead of using each slot for single IP, we would use an RIPE block of IP for one slot.

Slot 1 (64 IP)
Slot 2

Through this method, you would be able to obtain additional IP to be routed to your server. As we can see, we now have more than 64 IP, we used slot 1 to hold all 64 IP and slot 2 to hold 1 IP to make up 65 IPs in total on the server.

There is a total limit of 256 IP routed to an single server. You don’t have to use all the slots available, however you can use up to 64 slots overall. The 256 IP can be made up in any way on the server providing the server has less than 256 IP and has spare slots available.