Using Link Local Networking when DHCP Server is Not Available

FXR90 Integration Guide

If a DHCP server is not available, the reader can use Link Local networking to automatically provide a unique network IP address. The reader can then use TCP/IP to communicate with other computers also using a Link Local networking-generated IP address.

When using Link Local networking, the reader cannot communicate with computers on different subnets, or that do not use automatic private IP addressing. Automatic private IP addressing is enabled by default.

Use the Link Local networking procedure when the reader is connected directly to a PC. It reduces the overhead needed to configure the reader to a static IP address.

When Link Local networking executes after failing to detect a DHCP server, the reader automatically assigns an IPv4 IP address to the Ethernet interface in the form

169.254.xxx.xxx.

This IP address is predictable because it uses the last 2 bytes of the MAC address, usually represented as HEX values, to complete the IPv4 address. These values are converted to decimal format (for example, if the MAC address ends with

55:9A

, the IPv4 address assigned by the Link Local algorithm is

169.254.85.148

Windows-based computers support APIPA/Link Local networking by default when DHCP fails. To enable APIPA for a Windows PC, go to support.microsoft.com/ and search for APIPA.