Dynamic Host Client Protocol (DHCP)
DHCP is a protocol that gives units connected to a LAN the ability to ask a DHCP server which IP address to use. Therefore, the DHCP server is responsible for keeping track of which IP addresses are in use. For a unit to be able to ask the DHCP server for an IP address, it must support the DHCP protocol. Almost all devices support this protocol, but check the units user manual to verify this.
There are a few important things to keep in mind when you use the DHCP protocol. When DHCP is used, the IP address of a unit can change over time, although this does not normally happen. But if this happens and you a have a control system and touch panel connected, you might end up losing connection between the two.
However, if the DHCP is restarted or the IP range is changed, then the IP addresses assigned to each unit may be affected. If the IP address of a particular unit changes, it will no longer be able to connect to the network.
For example, if you test an installation at the office and save the IP addresses assigned by the office DHCP server and then hand over the units to the customer, then the customer’s LAN will either assign new IP addresses to the units using a DHCP protocol, or a network administrator will have to manually configure new static IP addresses. Since these addresses will be different from the addresses saved in the system settings, the units will not communicate. This means that if you want to prepare a customer installation at the office, you need to configure the office DHCP server to give the same address as the one at the customer’s location.
The advantage of DHCP is that it allows mobile equipment such as laptops and smartphones to connect to any LAN without needing to know anything about the LAN settings prior to connecting. Many applications also have a “lookup service” that searches the LAN for IP addresses of the devices connected to the network.
If you need to know the IP address of your units, we recommended that you use static IP addresses and reserve these IP addresses on the DHCP server so that it doesn’t assign them to other devices.