Lantronix XPress DR+ - Manual (Page 106)

XPress DR+ User Guide 106
Appendix C: Alternative Methods of Assigning
an IP Address
Earlier chapters describe how to assign a static IP address using DeviceInstaller, Web-
Manager, and Setup Mode (through a Telnet or serial connection). This section covers
other methods for assigning an IP address over the network.
DHCP
The unit ships with a default IP address of 0.0.0.0, which automatically enables DHCP. If
a DHCP server exists on the network, it provides the unit with an
IP address, gateway address, and subnet mask when the unit boots up.
You can use the DeviceInstaller software (if applicable) to search the network for the
DHCP-assigned IP address and add it to the list of devices retrieved.
Note: This DHCP address does not appear in the unit’s Setup Mode or in Web
Manager. You can determine your unit’s DHCP-assigned IP address in Monitor
Mode. When you enter Monitor Mode from the serial port with network
connection enabled and issue the NC (Network Communication) command, you
see the unit’s IP configuration.
AutoIP
The unit ships with a default IP address of 0.0.0.0, which automatically enables
Auto IP within the unit. AutoIP is an alternative to DHCP that allows hosts to obtain an IP
address automatically in smaller networks that may not have a DHCP server. A range of
IP addresses (from 169.254.0.1 to 169.254.255.1) has been explicitly reserved for
AutoIP-enabled devices. Do not use this range of Auto IP addresses over the Internet.
‹ If your unit cannot find a DHCP server, and you have not manually assigned an IP
address to it, the unit automatically selects an address from the AutoIP reserved
range. Then, your unit sends out a (ARP) request to other nodes on the same
network to see whether the selected address is being used.
‹ If the selected address is not in use, the unit uses it for local subnet communication.
‹ If another device is using the selected IP address, the unit selects another address
from the AutoIP range and reboots. After reboot, the unit sends out another ARP
request to see if the selected address is in use, and so on.
AutoIP does not replace DHCP. The unit continues to look for a DHCP server on the
network. If it finds a DHCP server, the unit switches to the DHCP server-provided
address and reboots.
Note: If a DHCP server is found, but it denies the request for an IP address, the
unit does not attach to the network, but waits and retries.