SDS1100 User Guide
2: Getting Started
DHCP
The unit ships with a default IP address of 0.0.0.0, which automatically enables
DHCP.
Provided a DHCP server exists on the network, it will provide the unit with an IP
address, gateway address, and subnet mask when the unit boots up. The SDS1100
has acquired an IP address if the red LED stops flashing and the green Status LED is
on continuously. (If no DHCP server exists, the unit responds with a diagnostic error:
the red Diagnostic LED blinks continuously, and the green Status LED blinks five
times. This blinking only continues for about 15 seconds.)
You can use the DeviceInstaller software to search the network for the IP your unit
has been assigned by the DHCP server and add it to the managed list. See
Add the
Unit to the Manage List
later in this chapter.
Note:
This DHCP address will not appear in the unit’s standard
configuration screens. You can, however, determine your unit’s DHCP-
assigned IP address in Monitor Mode. When you enter Monitor Mode from
the serial port with network connection enabled (see
Monitor Mode
in the
Troubleshooting chapter) and issue the NC (Network Communication)
command, you will 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 automatically
obtain an IP address 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. The range of Auto IP addresses is
not
to be used 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, then 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 itself. After reboot, the unit sends
out another ARP request to see if the selected address is in use, and so on.
AutoIP is not intended to replace DHCP. The unit will continue to look for a DHCP
server on the network. If a DHCP server is found, the unit will switch to the DHCP
server-provided address and reboot.
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.
AutoIP can be disabled by setting the unit’s IP address to 0.0.1.0. This setting
enables DHCP but disables AutoIP.
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