Terramaster F2-421 has 4 lan port 2xRealtek 8111F (uses r8168 driver) and 2xRealtek 8152 (uses r8153 driver).
I enabled other 2 Realtek 8152 (r8153) lan ports and tested them, they behaves same like r8168.
During playing settings I noticed something strange; if I change MTU (value doesn't matter) value of LAN port on Control Panel of DSM, iperf3 reports full gigabit speed (around 949 Mbits/sec) of lan port initially. But after DSM restarts somethings (maybe some services???) again reports slow and unstable speeds.
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Server listening on 5201
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Accepted connection from 10.10.2.51, port 59879
[ 5] local 10.10.2.12 port 5201 connected to 10.10.2.51 port 59885
[ ID] Interval Transfer Bitrate
[ 5] 0.00-1.00 sec 108 MBytes 905 Mbits/sec
[ 5] 1.00-2.00 sec 113 MBytes 949 Mbits/sec
[ 5] 2.00-3.00 sec 113 MBytes 949 Mbits/sec
[ 5] 3.00-4.00 sec 113 MBytes 949 Mbits/sec
[ 5] 4.00-5.00 sec 111 MBytes 933 Mbits/sec
[ 5] 5.00-6.00 sec 63.0 MBytes 528 Mbits/sec
[ 5] 6.00-7.00 sec 10.6 MBytes 89.2 Mbits/sec
[ 5] 7.00-8.00 sec 23.0 MBytes 193 Mbits/sec
[ 5] 8.00-9.00 sec 2.23 MBytes 18.7 Mbits/sec
[ 5] 9.00-10.00 sec 8.79 MBytes 73.8 Mbits/sec
[ 5] 10.00-10.20 sec 156 KBytes 6.39 Mbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate
[ 5] 0.00-10.20 sec 666 MBytes 548 Mbits/sec receiver
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Server listening on 5201
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I booted F2-421 with Terramaster's official TOS and Manjaro live USB, then repeated iperf3 tests. All 4 ports of device were OK and gives full gigabit speed. So there is no hardware problem.
I really need help, please.
Thanks.