Flint 2 GL-MT6000 caps WAN speed to 1gbps

dgsound · July 14, 2026, 9:15am

I’ve recently changed ISP to a FTTH 2.5/1 gbps connection with ISP own router that provides DHCP connection to my Flint 2 using a CAT 8 cable to both 2.5 gbps ports.

To my surprise, Flint 2 never reaches 2.5 gbps download speed.

root@GL-MT6000:~# iperf3 -c speed-cb.dimensione.com -p 5201-5209
Connecting to host speed-cb.dimensione.com, port 5201
[  5] local 192.168.1.2 port 50888 connected to 185.152.44.54 port 5201
[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
[  5]   0.00-1.00   sec  35.4 MBytes   297 Mbits/sec    0   1.95 MBytes
[  5]   1.00-2.00   sec   115 MBytes   965 Mbits/sec    0   3.70 MBytes
[  5]   2.00-3.00   sec   118 MBytes   986 Mbits/sec    0   3.70 MBytes
[  5]   3.00-4.00   sec   118 MBytes   986 Mbits/sec    0   3.70 MBytes
[  5]   4.00-5.00   sec   118 MBytes   986 Mbits/sec    0   3.70 MBytes
[  5]   5.00-6.00   sec   118 MBytes   986 Mbits/sec    0   3.70 MBytes
[  5]   6.00-7.00   sec   118 MBytes   986 Mbits/sec    0   3.70 MBytes
[  5]   7.00-8.00   sec   118 MBytes   986 Mbits/sec    0   3.70 MBytes
[  5]   8.00-9.00   sec   118 MBytes   986 Mbits/sec    0   3.70 MBytes
[  5]   9.00-10.00  sec   116 MBytes   975 Mbits/sec    0   3.70 MBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.00  sec  1.06 GBytes   914 Mbits/sec    0             sender
[  5]   0.00-10.02  sec  1.06 GBytes   912 Mbits/sec                  receiver

iperf Done.

I’ve tried many firmwares (4.8.2, 4.9.0, 4.8.2-op24, 4.9.1-op25, actual one is 4.9.0 13/7 snapshot) and every time connection is capped to 1gbps.

I’ve checked also ethtool

root@GL-MT6000:~# ethtool eth1
Settings for eth1:
        Supported ports: [ TP MII ]
        Supported link modes:   10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
                                1000baseT/Full
                                2500baseT/Full
        Supported pause frame use: Symmetric Receive-only
        Supports auto-negotiation: Yes
        Supported FEC modes: Not reported
        Advertised link modes:  10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
                                1000baseT/Full
                                2500baseT/Full
        Advertised pause frame use: Symmetric Receive-only
        Advertised auto-negotiation: Yes
        Advertised FEC modes: Not reported
        Link partner advertised link modes:  10baseT/Half 10baseT/Full
                                             100baseT/Half 100baseT/Full
                                             1000baseT/Full
                                             2500baseT/Full
        Link partner advertised pause frame use: Symmetric Receive-only
        Link partner advertised auto-negotiation: Yes
        Link partner advertised FEC modes: Not reported
        Speed: 2500Mb/s
        Duplex: Full
        Port: MII
        PHYAD: 1
        Transceiver: external
        Auto-negotiation: on
        Current message level: 0x000000ff (255)
                               drv probe link timer ifdown ifup rx_err tx_err
        Link detected: yes

and it clearly states that 2.5 gbps connection is negotiated with ISP router.

Futhermore using iperf reverse mode I reach advertised speeds:

root@GL-MT6000:~# iperf3 -c speed-cb.dimensione.com -p 5201-5209 -P 8 -R
Connecting to host speed-cb.dimensione.com, port 5201
Reverse mode, remote host speed-cb.dimensione.com is sending
[  5] local 192.168.1.2 port 51478 connected to 185.152.44.54 port 5201
[  7] local 192.168.1.2 port 51488 connected to 185.152.44.54 port 5201
[  9] local 192.168.1.2 port 51498 connected to 185.152.44.54 port 5201
[ 11] local 192.168.1.2 port 51506 connected to 185.152.44.54 port 5201
[ 13] local 192.168.1.2 port 51522 connected to 185.152.44.54 port 5201
[ 15] local 192.168.1.2 port 51524 connected to 185.152.44.54 port 5201
[ 17] local 192.168.1.2 port 51536 connected to 185.152.44.54 port 5201
[ 19] local 192.168.1.2 port 51552 connected to 185.152.44.54 port 5201
[ ID] Interval           Transfer     Bitrate
[  5]   0.00-1.00   sec  20.2 MBytes   170 Mbits/sec
[  7]   0.00-1.00   sec  24.3 MBytes   204 Mbits/sec
[  9]   0.00-1.00   sec  26.4 MBytes   221 Mbits/sec
[ 11]   0.00-1.00   sec  17.7 MBytes   148 Mbits/sec
[ 13]   0.00-1.00   sec  34.2 MBytes   287 Mbits/sec
[ 15]   0.00-1.00   sec  24.3 MBytes   204 Mbits/sec
[ 17]   0.00-1.00   sec  22.0 MBytes   184 Mbits/sec
[ 19]   0.00-1.00   sec  28.5 MBytes   239 Mbits/sec
[SUM]   0.00-1.00   sec   198 MBytes  1.66 Gbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[  5]   1.00-2.00   sec  24.2 MBytes   203 Mbits/sec
[  7]   1.00-2.00   sec  28.9 MBytes   243 Mbits/sec
[  9]   1.00-2.00   sec  27.7 MBytes   232 Mbits/sec
[ 11]   1.00-2.00   sec  20.4 MBytes   171 Mbits/sec
[ 13]   1.00-2.00   sec  46.3 MBytes   389 Mbits/sec
[ 15]   1.00-2.00   sec  25.4 MBytes   213 Mbits/sec
[ 17]   1.00-2.00   sec  24.6 MBytes   206 Mbits/sec
[ 19]   1.00-2.00   sec  35.6 MBytes   298 Mbits/sec
[SUM]   1.00-2.00   sec   233 MBytes  1.95 Gbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[  5]   2.00-3.00   sec  28.1 MBytes   236 Mbits/sec
[  7]   2.00-3.00   sec  31.4 MBytes   264 Mbits/sec
[  9]   2.00-3.00   sec  35.1 MBytes   295 Mbits/sec
[ 11]   2.00-3.00   sec  23.6 MBytes   198 Mbits/sec
[ 13]   2.00-3.00   sec  42.4 MBytes   356 Mbits/sec
[ 15]   2.00-3.00   sec  28.8 MBytes   242 Mbits/sec
[ 17]   2.00-3.00   sec  26.0 MBytes   218 Mbits/sec
[ 19]   2.00-3.00   sec  32.8 MBytes   276 Mbits/sec
[SUM]   2.00-3.00   sec   248 MBytes  2.08 Gbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[  5]   3.00-4.00   sec  28.0 MBytes   234 Mbits/sec
[  7]   3.00-4.00   sec  28.2 MBytes   236 Mbits/sec
[  9]   3.00-4.00   sec  26.9 MBytes   225 Mbits/sec
[ 11]   3.00-4.00   sec  25.3 MBytes   212 Mbits/sec
[ 13]   3.00-4.00   sec  33.6 MBytes   281 Mbits/sec
[ 15]   3.00-4.00   sec  33.2 MBytes   279 Mbits/sec
[ 17]   3.00-4.00   sec  30.0 MBytes   251 Mbits/sec
[ 19]   3.00-4.00   sec  30.1 MBytes   252 Mbits/sec
[SUM]   3.00-4.00   sec   235 MBytes  1.97 Gbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[  5]   4.00-5.00   sec  25.1 MBytes   211 Mbits/sec
[  7]   4.00-5.00   sec  25.4 MBytes   213 Mbits/sec
[  9]   4.00-5.00   sec  25.0 MBytes   210 Mbits/sec
[ 11]   4.00-5.00   sec  24.6 MBytes   206 Mbits/sec
[ 13]   4.00-5.00   sec  29.8 MBytes   250 Mbits/sec
[ 15]   4.00-5.00   sec  30.6 MBytes   257 Mbits/sec
[ 17]   4.00-5.00   sec  25.2 MBytes   212 Mbits/sec
[ 19]   4.00-5.00   sec  27.5 MBytes   231 Mbits/sec
[SUM]   4.00-5.00   sec   213 MBytes  1.79 Gbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[  5]   5.00-6.00   sec  23.1 MBytes   194 Mbits/sec
[  7]   5.00-6.00   sec  26.3 MBytes   220 Mbits/sec
[  9]   5.00-6.00   sec  33.8 MBytes   283 Mbits/sec
[ 11]   5.00-6.00   sec  27.5 MBytes   230 Mbits/sec
[ 13]   5.00-6.00   sec  31.6 MBytes   265 Mbits/sec
[ 15]   5.00-6.00   sec  33.8 MBytes   283 Mbits/sec
[ 17]   5.00-6.00   sec  28.5 MBytes   239 Mbits/sec
[ 19]   5.00-6.00   sec  28.6 MBytes   240 Mbits/sec
[SUM]   5.00-6.00   sec   233 MBytes  1.96 Gbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[  5]   6.00-7.00   sec  23.7 MBytes   198 Mbits/sec
[  7]   6.00-7.00   sec  25.9 MBytes   217 Mbits/sec
[  9]   6.00-7.00   sec  32.7 MBytes   275 Mbits/sec
[ 11]   6.00-7.00   sec  25.7 MBytes   216 Mbits/sec
[ 13]   6.00-7.00   sec  33.6 MBytes   282 Mbits/sec
[ 15]   6.00-7.00   sec  33.1 MBytes   278 Mbits/sec
[ 17]   6.00-7.00   sec  27.5 MBytes   231 Mbits/sec
[ 19]   6.00-7.00   sec  27.7 MBytes   232 Mbits/sec
[SUM]   6.00-7.00   sec   230 MBytes  1.93 Gbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[  5]   7.00-8.00   sec  24.7 MBytes   207 Mbits/sec
[  7]   7.00-8.00   sec  26.5 MBytes   222 Mbits/sec
[  9]   7.00-8.00   sec  32.0 MBytes   268 Mbits/sec
[ 11]   7.00-8.00   sec  27.3 MBytes   229 Mbits/sec
[ 13]   7.00-8.00   sec  34.7 MBytes   291 Mbits/sec
[ 15]   7.00-8.00   sec  32.3 MBytes   271 Mbits/sec
[ 17]   7.00-8.00   sec  27.6 MBytes   232 Mbits/sec
[ 19]   7.00-8.00   sec  23.5 MBytes   197 Mbits/sec
[SUM]   7.00-8.00   sec   229 MBytes  1.92 Gbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[  5]   8.00-9.00   sec  26.4 MBytes   222 Mbits/sec
[  7]   8.00-9.00   sec  26.4 MBytes   221 Mbits/sec
[  9]   8.00-9.00   sec  31.5 MBytes   265 Mbits/sec
[ 11]   8.00-9.00   sec  26.7 MBytes   224 Mbits/sec
[ 13]   8.00-9.00   sec  36.5 MBytes   306 Mbits/sec
[ 15]   8.00-9.00   sec  31.5 MBytes   264 Mbits/sec
[ 17]   8.00-9.00   sec  25.4 MBytes   213 Mbits/sec
[ 19]   8.00-9.00   sec  24.2 MBytes   203 Mbits/sec
[SUM]   8.00-9.00   sec   229 MBytes  1.92 Gbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[  5]   9.00-10.00  sec  26.0 MBytes   218 Mbits/sec
[  7]   9.00-10.00  sec  24.7 MBytes   208 Mbits/sec
[  9]   9.00-10.00  sec  31.9 MBytes   268 Mbits/sec
[ 11]   9.00-10.00  sec  25.4 MBytes   213 Mbits/sec
[ 13]   9.00-10.00  sec  36.9 MBytes   310 Mbits/sec
[ 15]   9.00-10.00  sec  31.6 MBytes   265 Mbits/sec
[ 17]   9.00-10.00  sec  22.8 MBytes   192 Mbits/sec
[ 19]   9.00-10.00  sec  27.8 MBytes   233 Mbits/sec
[SUM]   9.00-10.00  sec   227 MBytes  1.91 Gbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.03  sec   254 MBytes   213 Mbits/sec  23472             sender
[  5]   0.00-10.00  sec   249 MBytes   209 Mbits/sec                  receiver
[  7]   0.00-10.03  sec   274 MBytes   229 Mbits/sec  26519             sender
[  7]   0.00-10.00  sec   268 MBytes   225 Mbits/sec                  receiver
[  9]   0.00-10.03  sec   320 MBytes   268 Mbits/sec  27633             sender
[  9]   0.00-10.00  sec   303 MBytes   254 Mbits/sec                  receiver
[ 11]   0.00-10.03  sec   250 MBytes   209 Mbits/sec  22852             sender
[ 11]   0.00-10.00  sec   244 MBytes   205 Mbits/sec                  receiver
[ 13]   0.00-10.03  sec   379 MBytes   317 Mbits/sec  34124             sender
[ 13]   0.00-10.00  sec   360 MBytes   302 Mbits/sec                  receiver
[ 15]   0.00-10.03  sec   323 MBytes   270 Mbits/sec  29093             sender
[ 15]   0.00-10.00  sec   305 MBytes   256 Mbits/sec                  receiver
[ 17]   0.00-10.03  sec   267 MBytes   223 Mbits/sec  23765             sender
[ 17]   0.00-10.00  sec   260 MBytes   218 Mbits/sec                  receiver
[ 19]   0.00-10.03  sec   295 MBytes   247 Mbits/sec  26034             sender
[ 19]   0.00-10.00  sec   286 MBytes   240 Mbits/sec                  receiver
[SUM]   0.00-10.03  sec  2.31 GBytes  1.98 Gbits/sec  213492             sender
[SUM]   0.00-10.00  sec  2.22 GBytes  1.91 Gbits/sec                  receiver

iperf Done.

Tested both HW acc on/off, SW acc on/off with no meaningful changes and HTOP doesn’t show any bottlenecks. VPN is active only for a few sites and even when turned off speed is still capped.

I’m asking for help to get my clients reaching advertised internet speeds of my connection.
Thanks

will.qiu · July 14, 2026, 9:28am

Hi,

Thank you for your question.

Please note that iperf3 Reverse mode is the correct way to measure the download speed from the local host's perspective.

You can see the difference from the following message:

Reverse mode, remote host speed-cb.dimensione.com is sending

Based on your results, both the download and upload speeds appear to be consistent with the 2.5 Gbps download / 1 Gbps upload service provided by your ISP.

We also recommend testing with websites such as Speedtest.net, as they provide a more intuitive view of your Internet connection performance.

dgsound · July 14, 2026, 9:45am

Using python-speedtest-cli download speed is lower than 1gbps at best (tried multiple servers, I’m showing the best one):

Hosted by Iliad Italia S.p.A. (Milan): 34.587 ms
Testing download speed................................................................................
Download: 759.34 Mbit/s
Skipping upload test

If you have any other suggestions to measure router speeds inside SSH (as my clients always show nearly 1Gbps download speed) I’m glad to hear it.
Thank you for your help

will.qiu · July 14, 2026, 9:55am

You could also try the official Speedtest CLI written in C. The Python version is unofficial and appears to have some performance issues.

wget https://install.speedtest.net/app/cli/ookla-speedtest-1.2.0-linux-aarch64.tgz
tar -xzf ookla-speedtest-1.2.0-linux-aarch64.tgz speedtest
./speedtest

dgsound · July 14, 2026, 9:58am

Thank you, that helped me measuring the best currently:

Idle Latency:     2.99 ms   (jitter: 0.14ms, low: 2.85ms, high: 3.33ms)
    Download:  2205.74 Mbps (data used: 2.0 GB)
                 10.17 ms   (jitter: 16.18ms, low: 3.16ms, high: 254.18ms)
      Upload:   979.29 Mbps (data used: 772.3 MB)
                 16.82 ms   (jitter: 1.11ms, low: 4.61ms, high: 20.43ms)
 Packet Loss:     0.0%

Now I need to check if I can improve Wi-Fi performance for my clients, but otherwise I’m glad that I could see that it’s working fine now.
Thank you for your support