I generally recommend static DHCP leases over static IP addresses for almost any circumstance.
There are three primary reasons for that:
- DHCP will automatically configure gateway, DNS servers and other options – if you change your network configuration, this will avoid having to reconfigure your devices with static IP addresses.
- Monitoring capability: You’ll be able to see if a device has requested the IP address from the DHCP server. This also means that you have an easy way
- Failure tolerance: If you connect the device to the wrong network – for example, if you connect it to the wrong VLAN – it will still try to acquire an IP address. which you can see in the DHCP lease table of the router. This is often relevant when, for example, changing network components or moving equipment between locations. Quite often, it’s hard to access equipment that has an unknown IP address and a complete reset would also delete a lot of configuration work.
There are cases however, where a static IP address should be preferred:
- DHCP server needs static IP: If the device is the DHCP server itself, obviously you need to set a static IP address (only on the interface where the DHCP server is enabled, of course)
- Reliability: If the device is mission-critical, you might not want to depend on the DHCP server being online. You need to weigh this argument against the failure tolerance and monitoring capability arguments as listed above! Note than some devices will only try to acquire an IP address using DHCP once and will not retry if no DHCP server answers!
- Network without DHCP server: If there is no DHCP server on the local network, obviously you need a static IP
- Dynamic MAC address: If a device doesn’t use the same MAC address all the time
If your device supports DHCP with fallback, I recomend that you use a static lease plus a static IP fallback with the same IP address. This approach can combine the advantages of both static leases and static IP addresses.