Beryl 7 (GL-MT3600BE) - TX speeds unstable

Routers
1

Hi there,

Could someone with a Beryl 7 (GL-MT3600BE) please run an iperf test on the LAN port and share their results?

I’m seeing a very strange issue. No matter how I configure the Beryl (router mode, AP/bridge mode, with or without DHCP, just forwarding traffic, etc.), I get very bad upload speeds when connecting to another wired device on the network.

Example via the Beryl:

[  5][TX-C]   0.00-3.90 sec  33.5 MBytes  72.1 Mbits/sec  sender
[  7][RX-C]   0.00-3.90 sec  438 MBytes   942 Mbits/sec   receiver

So:

  • Upload (client → LAN) ≈ 70–80 Mbit/s

  • Download (LAN → client) ≈ 900+ Mbit/s

Very asymmetric.

This does not happen when:

  • The same client is plugged directly into the main router

  • Or when using a different AP (Cudy WR3000 in my case)

Directly connected (no Beryl), I get:

[  5][TX-C]   0.00-10.00 sec  2.73 GBytes  2.34 Gbits/sec  sender
[  7][RX-C]   0.00-10.00 sec  1.09 GBytes   939 Mbits/sec  sender

So the physical cable and general network path are fine.

On the Beryl side I checked interface stats and I’m seeing a huge amount of FCS errors on the LAN port:

ethtool -S eth1 | egrep -i 'crc|fcs|err|drop|pause|disc|over'

rx_overflow: 0
rx_fcs_errors: 260393
rx_short_errors: 0
rx_long_errors: 0
rx_checksum_errors: 0

The rx_fcs_errors counter keeps increasing under load.

The LAN link negotiates at 2.5G full duplex, EEE is disabled, and I’ve tested with a different power supply (even a power bank) to rule out electrical noise — same behaviour.

Since the exact same cable and setup works perfectly when bypassing the Beryl, this makes me suspect:

  • A faulty LAN port on the unit?

  • 2.5G PHY instability?

  • A driver issue in the current firmware?

Has anyone seen similar behaviour on the Beryl 7 / MT7987 platform?

Would you recommend forcing the LAN port to 1G, updating firmware, or just RMA?

Any suggestions are welcome.

Cheers

2

When you say on the LAN port do you mean with iPerf running on the device itself? I’ve done various tests on mine through the device and get no issues like this with performance, but not with iperf on the device itself.

Can you give a bit more clarfication on the topology/setup where you see the performance issue that caused you to start testing? It’s not clear (to me anyway) when you say ‘to another wired device’ what you mean?

3

I had a similar experience.

But when troubleshooting thoroughly I figured that my network cable was still broken.

Brume 3 same cable works, Beryl 7 had the exact symptoms as your post.

My conclusion was that this device is alot more sensitive to bad cables, I did not even know that could be a thing.

Since I make most of my cables I went with a shielded rj45, rather than a shield rj45 ez plug.

After having a bad batch of those ez ones and moving in into my new house I had the weirdest issues, even had a 20 meter cable performing well for 6 months and suddenly broke, also my normal diagnosis failed with pinging and checking latency none gave me a indication of breakage, basicly the copper plating internal was lose on those plugs and the way the rubber terminates were both an issue.

I really don't trust these ez plugs one bit for stability, so for me it was easy to know it was broken, stability returned with the classic rj45.

I'm also thinking about this whole situation that maybe the exposed copper from such plug could start interfere too with some of the internal hardware behind the port, which can explain some very strange behaviours with errors, I don't know if you use such plugs on this cable? ( The difference is if the top has holes passthrough the cores (ez) exposed to air, or when it is air tight no holes (classic) )

4

@oorweeg No I mean iperf running on another machine downstream. Multiple other machines in fact the general topology is the following

Gaming PC (iperf client)
→ Beryl LAN port (eth1) vlan 10 untagged
→ (Beryl config: bridge/router, doesn’t really matter, happens either way)
→ Beryl WAN port (eth0) - tested vlan 10 tagged as well as vlan10 untagged - doesn’t make a difference

Then 2 other configurations tested
Config 1:
→ Layer 2 switch
→ target device (iperf server) (either another PC on the LAN or my NAS (both vlan 10))

Config 2:
→ 2.5G NIC on the main router (x86 machine running opnsense)
→ target device (iperf server) (either another PC on the LAN or my NAS (both vlan 10))

In both cases when i put the beryl in the chain the upload drops.
If i remove the beryl i get 1G or 2.5G depending on which configuration since the L2 switch i have is 1G and i get 2.5G if i connect it to the other interface on the main router.

@xize11 Oook I mean as you say I have also not really had the experience of a specific device being more or less sensitive to cables but i guess easy to test solution i can do on the weekend is to just bring both PC`s next to the main router plug them in directly and see i something changes.

Still tho how bad can this cable be that it goes from 2.5G without the beryl to <100M with it

5

In my case the faulty cable was smaller than a meter, I do know on sites like aliexpress they also sell cheap cables and some come also with these rj45 ez plugs attached, I really advise to use cables not having those.

6

It doesn’t need to be that bad, you only need a minimal amount of loss (maybe even 0.1 or 0.01% depending on latency and other factors) to totally tank throughput. Although that loss can be coming from the cable or somewhere else.

7

Hmm ok let’s see.

I mean all my cables are self made using normal connectors on a cat7 cable. But I will do the test with another cable and the machines closer together and then write back. I mean if that fixes it it would be a first for me but as @xize11 is saying apparently possible. Still kind of my head doesnt fit how can 1 router do full speed no problems on the same cable and then the other one crashes but eh well - im open to surprises :smiley:

8

Also this was my original post in case of interest.

I did some steps which led me to the conclusion it was the cable.

9

For what it’s worth but using shielded cables without the proper grounding intended for shielded cables can actually make things worse as the shielding acts like an antenna picking up interference which messes with the signal. The exact opposite of its intended purpose. Less of a problem on a short cable but something to keep in mind as you are often better off using cheaper cables to get better performance.

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