i have a cat5e cable that the router sets to 100Mb Full Duplex. Trying to set to 1000Mb makes port not work with that cable. Other cables works at 1000Mb full duplex on same port.
Only thing wrong here is that the cable is ftp but with utp rj45 connector.
ethtool declare speed 1000Mb
iperf max speed tested ~100Mb
the router declare port with max speed 100Mb.
Is it possible the wrong connector speeds down the cable?
Thanks
21 Answer
If you have a wiring issue on one (or both) end of the cable in pair 1-2 or pair 7-8 this is fairly normal.
The fall-back is 100 mb/s which only uses pairs 4-5 and 3-6.
Please note that if you want to set the speed manually you need to do so on BOTH devices on each end of the connection.
Ethernet auto-negotiate only works reliably if BOTH ends use auto-negotiate. If you want to set speed manually you need to go manual all the way.
With one side to auto and the other to manual you may get no connection at all, or you do get connection, but it will be unreliable (lot's of errors) and possibly not at the maximum speed.
