IP/25, can it be begin from xx.xx.xx.128, rather than xx.xx.xx.1?

Question

I have a dedicated server that I bought from a hosting company. This hosting company assigned me an IP address. However, I needed this dedicated server to use for different VPS servers. I have already split it and now all I need is to assign a valid ip address to each VPS server instead of local ip addresses. So, for example, I want to add 128 more IP addresses to my server.

I expected an IP list, but it resulted with a subnet.

I'm confused because I understand that the hosting company provides me with a subnet. For example, xx.xx.xx.xx/25. (In my contract, the maximum available IP address is limited to 128). I already know that IP is a 32-bit number and /25 is the last bit parts.

I mean, if the range of IP/24 is xx.xx.xx.1-xx.xx.xx.255 and the range of IP/25 is xx.xx.xx.1-xx.xx.xx.127.

Then what happens to the rest of the ip range xx.xx.xx.127-xx.xx.xx.255? I think it will never be used until I give my subnet back to the IP pool.

Or is it possible for someone else to use the rest? Then how should it be displayed, i.e. IP/24-2 or something else?

Answer 1

The address range for /24 is w.x.y.0 to w.x.y.255.

The address range for /25 is either w.x.y.0..127 or w.x.y.128..255.

A common notation is e.g. 192.168.0.129/25 for the first usable address in 192.168.0.128/25.

In an IPv4 subnet, the first (all host-part bits zero) and the last address (all host-part bits one) aren't usable for hosts. The former is by convention and the latter is the subnet's directed broadcast address.