Subnets are IP address areas that contain IP addresses. Subnets are normally specified based on the relevant subnet mask, which is a technically configured value on a network device that identifies the subnet. A subnet can then be divided into further areas, for example into sections for a specific customer or application scenarios within a subnet.
IP Address Management (IPAM)
Organization of IP addresses, subnets and ranges
Example
Subnet
A subnet can look as follows:
| Network-ID | from/to | Applied to |
| 172.22.0.0/16 | 172.22.0.1 – 172.22.255.255 | Location: Gersthofen, internal LAN |
Range
Although the technical subnet is predetermined, a subnet can then also be subdivided into further sections.
Possible examples for this scenario might be: Individual sections for departments, firewall rules, device types, and/or application areas:
Possible examples for this scenario might be: Individual sections for departments, firewall rules, device types, and/or application areas:
| Network-ID | from/to | Applied to |
| 172.22.0.0/24 | 172.22.0.1 – 172.22.0.254 | Routers/Switches |
| 172.22.1.0/24 | 172.22.1.1 – 172.22.1.254 | Servers |
| 172.22.2.0/24 | 172.22.2.1 – 172.22.2.254 | Printers |
IP Address
Once a range has been selected the corresponding IP addresses will be listed. This will identify which IP addresses have been issued and which are still available, where necessary with their hostname.
| 172.22.0.1 | active | ROUTER-01 |
| 172.22.0.2 | active | ROUTER-02 |
| 172.22.0.3 | active | SWITCH-01 |
It is also important to realize that not all subnets have to be – or indeed can be – divided into further sections. For example, you might have a transfer network which only consists of two possible IP addresses. For this reason, the setup described above only serves as an aide to understanding ERAMON’s IPAM.