I'm having a custom cable made that will only use 2 of the 4 pairs for Ethernet. I'm connecting a 10/100 Mbps device to a network with other GigE devices.
However, I have seen one similar adapter online that places a resistor across the unused pairs - (See second device).
Are those resistors necessary? If so, recommend resistance? Any further advice making 4-pair GigE and 2-pair 10/100 devices play nice?