Raritan Dominion KX II User Manual page 256

Appendix A: Specifications
248
Functions; not recommended
NOT supported by Ethernet specification; product will
communicate, but collisions will occur
Per Ethernet specification, these should be "no
communication," however, note that the Dominion KX II
behavior deviates from expected behavior
Note: For reliable network communication, configure the Dominion KX II
and the LAN switch to the same LAN Interface Speed and Duplex. For
example, configure both the Dominion KX II and LAN Switch to
Autodetect (recommended) or set both to a fixed speed/duplex such as
100MB/s/Full.