Please run iperf3 -c 127.0.0.1 and post results here to make router database

|MikroTik RB5009 | Marvell Armada 7040
(Quad Core A72, 1.4GHz) | Snapshot 6.1.79 |

root@RB5009UG:/tmp# ubus call system board
{
        "kernel": "6.1.79",
        "hostname": "RB5009UG",
        "system": "ARMv8 Processor rev 1",
        "model": "MikroTik RB5009",
        "board_name": "mikrotik,rb5009",
        "rootfs_type": "squashfs",
        "release": {
                "distribution": "OpenWrt",
                "version": "SNAPSHOT",
                "revision": "r25360-7777921aa0",
                "target": "mvebu/cortexa72",
                "description": "OpenWrt SNAPSHOT r25360-7777921aa0"
        }
}
OpenWrt SNAPSHOT, r25360-7777921aa0
 -----------------------------------------------------
root@RB5009UG:~# iperf3 -s -D && iperf3 -c 127.0.0.1
Connecting to host 127.0.0.1, port 5201
[  5] local 127.0.0.1 port 59828 connected to 127.0.0.1 port 5201
[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
[  5]   0.00-1.00   sec  1.12 GBytes  9.64 Gbits/sec    0   1.12 MBytes
[  5]   1.00-2.00   sec  1.05 GBytes  9.02 Gbits/sec    0   1.12 MBytes
[  5]   2.00-3.00   sec  1.11 GBytes  9.51 Gbits/sec    0   1.19 MBytes
[  5]   3.00-4.00   sec  1.03 GBytes  8.84 Gbits/sec    0   1.19 MBytes
[  5]   4.00-5.00   sec  1.09 GBytes  9.39 Gbits/sec    0   1.19 MBytes
[  5]   5.00-6.00   sec  1.08 GBytes  9.31 Gbits/sec    0   1.19 MBytes
[  5]   6.00-7.00   sec  1.07 GBytes  9.23 Gbits/sec    0   1.19 MBytes
[  5]   7.00-8.00   sec  1.07 GBytes  9.20 Gbits/sec    0   1.19 MBytes
[  5]   8.00-9.00   sec  1.07 GBytes  9.22 Gbits/sec    0   1.19 MBytes
[  5]   9.00-10.00  sec  1.07 GBytes  9.19 Gbits/sec    0   1.19 MBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.00  sec  10.8 GBytes  9.26 Gbits/sec    0             sender
[  5]   0.00-10.00  sec  10.8 GBytes  9.25 Gbits/sec                  receiver

iperf Done.