Public IP Subnet is a range of public IPs where 3 addresses are reserved for gateway, netmask and network configuration purposes.
What is an IP Subnet?
IP Subnet is a range of IP addresses that uses similar routing principles as Management IP addresses, yet there are some important differences.
IP Subnets come in ranges with a minimum amount of IP addresses included. The following ranges are available at the moment:
- /29 (8 IP addresses / )
- /28 (16 IP addresses)
- /27 (32 IP addresses)
- /26 (64 IP addresses)
When using an IP Subnet up to 3 IP addresses from its range are reserved for network configuration purposes. These 3 IP addresses are not available to use with your server application and are used as follows: 1 x Network IP, 1 x Gateway IP, 1 x Broadcast IP.
How does an IP Subnet work?
Let's say we have ordered an IP Subnet 203.0.113.0/29 that has 8 IP addresses. Its configuration will look as follows:
- 203.0.113.0 – Network IP address (unusable for services)
- 203.0.113.1 – Gateway IP address (unusable for services)
- 203.0.113.2, 203.0.113.3, 203.0.113.4, 203.0.113.5, 203.0.113.6 – Host IP (available on your system)
- 203.0.113.7 – Broadcast IP address (unusable for services)
This leaves you with 5 IP addresses available to use with your application. Network, gateway and broadcast IP addresses are essential to the routing of the IP Subnet, so they are always dedicated for network configuration purposes. The exact network topology of your IP Subnet is illustrated in the image below:
In addition to the Management IP address (198.51.100.10) an additional IP range is configured. When your server application uses the source address from your IP Subnet, it queries the Gateway IP address (203.0.113.1) of your IP Subnet, instead of the default Gateway IP address (198.51.100.1) of your server.
IP Subnets are not easily movable between servers, as it depends on where in the Cherry Servers data center do they reside. This means that after assigning one of the available IP addresses to a specific server, the client may not be able to assign the next available IP addresses to another server, if it resides in a different data center module. As IP Subnets are most often used with a hypervisor when creating virtual machines on a Dedicated Server, this may not be an issue.