The DHCP does not return an IP address when it is used with some third party devices.

Issue
The DHCP does not return an Ip address when it is used with some third party devices.

Product Line
All Unity Premium CoPro Ethernet product PLC's
All TSXETYzzzz modules
All Unity TSXP57zzzz Co-Processors.

Environment
Windows 7

Resolution
The DHCP server does not return an IP address when it is used with some third party devices. This can
occur if the size of the discover packet from the third party device is less than 576 bytes. The Unity Co-Pro
and Ethernetnet modules are designed to mee the requirments of RFC 2131. Discover packets from third
part devices that do not meet the requirement may get rejected.

The following is taken from the RFC2131:

The 'options' field is now variable length. A DHCP client must be prepared to receive DHCP messages
with an 'options' field of at least length 312 octets. This requirement implies that a DHCP client must be
prepared to receive a message of up to 576 octets, the minimum IP datagram size an IP host must be
prepared to accept [3]. DHCP clients may negotiate the use of larger DHCP messages through the
'maximum DHCP message size' option. The options field may be further extended into the 'file' and
'sname' fields.

To resolve the issue, the third party device must be to updated to meet the required minimum packet size
of 576 bytes.