GL.iNet Flint 2 (GL-MT6000) slow on network side

Installing and Using OpenWrt
1

Hey all, hoping someone here can sanity-check what’s going on with my GL.iNet Flint 2 (GL-MT6000).

ISP / Setup

  • Vodafone UK Gigafast 900 (FTTP via Openreach ONT)

  • Vodafone Power Hub → LAN1 → Flint 2 WAN

  • Flint 2 handles LAN, VPNs, firewall, etc.

  • Firmware: 4.8.3 (OpenWrt 21.02-snapshot)

  • Hardware acceleration ON, full-cone NAT enabled

  • NAT/DMZ on Vodafone exposing 192.168.1.128 (Flint WAN)

  • Flint LAN = 192.168.8.0/24

  • DHCP from Flint; Vodafone DHCP still on for its side

The issue

Vodafone’s router alone gives me:

~930 Mb/s down / 105 Mb/s up

When I run the speed test inside the Flint 2 (SSH shell) using iperf3, I also get full gigabit:

iperf3 -c iperf.as42831.net -p 5300-5400 -R
[  5]   0.00-10.00  sec  1.08 GBytes  927 Mbits/sec  receiver

So WAN → Flint is fine.

But any client (wired or Wi-Fi) through the Flint tops out around 300 Mb/s down, 95 Mb/s up.
That includes a laptop connected directly to a Flint LAN port over Cat 6.

Tests done

  • Verified Flint WAN IP = 192.168.1.128 via DHCP from Vodafone.

  • Ran iperf3 directly on Flint → full 930 Mb/s.

  • Ran PowerShell live speed monitor on laptop → ~300 Mb/s over Ethernet, 60–100 Mb/s over Wi-Fi.

  • Confirmed Network Acceleration = ON (Hardware Auto).

    • Full-cone NAT (on/off)

    • Software vs Hardware acceleration modes → No difference.

  • DNS set to Cloudflare (1.1.1.1 / 1.0.0.1)

  • No QoS/SQM, VPN, or IDS/IPS active.

  • Wi-Fi off for testing (wired only).

  • Cable → verified Cat 5e/6; direct to laptop gives 1 Gb/s link light.

Observed

  • Flint’s own iperf test: ~930 Mb/s

  • Laptop → Flint LAN port: ~300 Mb/s

  • Browser downloads from same machine: ~260–300 Mb/s

  • Nothing else drawing bandwidth.

Also, just connecting the GL.iNet Flint 2 (GL-MT6000) and omitting the Vodafone router and Double NAT DMZ setup gives the same results.

Goal

Find out what’s limiting LAN-side throughput on the Flint 2 when the router itself can saturate gigabit upstream.
Is there a known issue with OpenWrt 21.02 builds on the MT6000, or a hidden setting (offload module, bridge mode quirk, etc.) that caps LAN performance?

Any ideas, sysctl tweaks, or real-world configs from other Vodafone UK FTTP users would be hugely appreciated.

(Diagnostics run so far: iperf3*,* Get-NetAdapter*, PowerShell live throughput monitor, hardware acceleration toggles.)*

2

The firmware you're running is heavily modified by GL.iNet with proprietary SDK. Better to ask over in their forum.

2 Likes
3

It looks like you are using GL.INet's software instead of the Genuine OpenWRT

You should at least run OpenWRT 24.10.3

1 Like
4

Thanks, Dave, I did try over there, but not much joy. I thought it might be worth asking over here, where the knowledge base is probably wider.

5

It's not, as long as you're running the vendor firmware.

6

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