Debian Hardware :: Slow Outgoing Network Speed With RTL8111 / 8168B

I'm experiencing very slow network speeds in one direction (out) on a clean install of debian.

iperf client running on laptop connecting to server with issue:
Code: Select all$ iperf -c 192.168.10.187 -d
------------------------------------------------------------
Server listening on TCP port 5001
TCP window size:  128 KByte (default)
------------------------------------------------------------
------------------------------------------------------------
Client connecting to 192.168.10.187, TCP port 5001
TCP window size:  129 KByte (default)
------------------------------------------------------------
[  5] local 192.168.10.131 port 55340 connected with 192.168.10.187 port 5001
[  6] local 192.168.10.131 port 5001 connected with 192.168.10.187 port 52664
[ ID] Interval       Transfer     Bandwidth
[  5]  0.0-10.0 sec   247 MBytes   207 Mbits/sec
[  6]  0.0-11.5 sec  1.00 MBytes   730 Kbits/sec

I've tried with different cables on the server, no luck. Also note that the laptop gets full speed to speedtest.net as per my internet subscription (75/75 gbit fiber), so the laptop can be ruled out as a problem since it gets more than 75X performance to the internet compared to the local server.

The main purpose of this server is to be a virtualbox host. I've set up one guest system and ran iperf between the host/guest (bridged network). It gives better numbers, still the host -> guest direction is much slower than it should be:

Code: Select allClient connecting to 192.168.10.187, TCP port 5001
TCP window size:  108 KByte (default)
------------------------------------------------------------
[  3] local 192.168.10.163 port 48573 connected with 192.168.10.187 port 5001
[  5] local 192.168.10.163 port 5001 connected with 192.168.10.187 port 48856
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-10.0 sec  1.65 GBytes  1.42 Gbits/sec

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