HP EliteBook 840 G7 limited ethernet speed on USB-C docking station

[wielorybus]

My set: HP Elitebook 840 G7 + USB-C/A Universal Dock G2 (same issue on USB-C/A Universal Dock G5) has a problem with ethernet speed. The link shows 1Gb/s but iperf to local server in local network shows only ~300Mb/s:

Client connecting to dc, TCP port 5001
TCP window size: 512 KByte (default)
------------------------------------------------------------
[ 3] local 192.168.1.11 port 57420 connected with 192.168.1.2 port 5001
[ ID] Interval Transfer Bandwidth
[ 3] 0.0-10.0 sec 374 MBytes 314 Mbits/sec

Checked on Windows 10 / Linux. Other laptop on the same network cable works OK up to 1Gb/s. The issue is with USB-C/A dock station or the laptop itself.

[wielorybus]

Update - I've checked it on two more docking station (DELL + Kensignton) and the problem is still visible. That means the problem is with the laptop itself, not USB-C docking station.