An EL device retains a source (its own) IP and MAC address and destination IP and MAC address in nonvolatile memory. The destination addresses are defined as the address the EL device will send Ethernet data. If the data is to be sent to only one computer, the destination address will be the IP and MAC address of that computer. However, it is usually desirable for the EL device to send data to all the computers in a network. In that case, the special IP address of 255.255.255.255 and a MAC address of FF-FF-FF-FF-FFFF are used. These are called “broadcast” addresses.

By default, an EL device has its own IP address (source address) set to 192.168.0.90. Typically, the “subnet” of a LAN will be defined by the first three groups of digits in the IP address (i.e. 192.168.0) of a device connected to the LAN. In this case, the IP addresses of all computers and devices located on a router will have these first three groups of digits the same. During setup, the EL source IP address should be changed to match the subnet. The last group (i.e. 90) can be set to any unique number except 255 or 0, but should be configured to a static IP within the router or set outside the range of the router’s DHCP server. More information on DHCP ranges in routers and subnet identification can be found below in Appendix B, Routers and IP address Assignment.