BBS: TELESC.NET.BR
Assunto: Re: Uodate on PI wifi bridging issues.
De: Tauno Voipio
Data: Thu, 5 Feb 2026 21:44:08 +0200
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On 5.2.2026 16.27, The Natural Philosopher wrote:
> On 05/02/2026 14:04, Lars Poulsen wrote:
>> On 2026-02-04, The Natural Philosopher wrote:
>>> If you remember I had constricted a bridge from wifi to ethernet to act
>>> as a bridged access point. On a PI 4B as a test platform
>>>
>>> The problem was that whilst the bridge was reasonably OK accessing my
>>> LAN, up to 90% packet loss was experienced when accessing the internet
>>> via my edge router.
>>>
>>> Two further points have been established but the exact reason for the
>>> behaviour still remains a mystery
>>>
>>> 1/. A friend with a Pi 5 attempted to duplicate the setup, could not get
>>> it to work and instead used the Network Manager GUI to set up a
>>> (routed?) access point which worked ok. It turns out that you cannot use
>>> the GUI tool to set up a bridge at all. Only nmcli.
>>>
>>> 2/. After a long time with traceroutes and pings I realised that this
>>> particular machine was the *only one wired directly to the router via a
>>> single gigabit Ethernet cable*. Everything else went via an ancient
>>> 100Mbps switch that I inherited from an office clearout. In a rash of
>>> 'well I tried everything else' I unplugged the Pi from the Gigabit
>>> router socket and put it into the 100Mbps switch and bingo!... Pretty
>>> decent internet performance. Yes extremely long transfers sometimes
>>> fail, but its very useable
>>>
>>> What I cannot for the life of me understand is *why* this worked. The
>>> same [Gigabit] link was involved in both local and Internet access. The
>>> only difference being that local access ALSO went through a 100Mbps
>>> switch.
>>>
>>> If anyone can shed light on this I would appreciate it.
>>>
>>> If it matters, the router is a Draytek Vigor2762Vac running PPPoE via an
>>> Openrach ONT to an optical fibre for Internet and thence to the ISP.
>>
>> The link-level connection involves a negotiation handshake to find
>> compatible parameters. You may read up on MII (Media Independent
>> Interface). When the state machines in the MII part of the MAC block in
>> the Ethernet part of your SoC chip encounters an MII state machine it
>> has not seen before, there may be timing dependent glitches.
>> One of our customers has an installation on a remote island where
>> the link between a microprocessor in his seismic gear connected via an
>> ethernet switch to our radio locks up every 6 to 12 months and needs a
>> remote-triggered power cycle to reset. We suggested he try another
>> switch next time he can get a service tech to the island.
>>
>> It is also possible that a port data rate of a Gigabit may occasionally
>> cause bus contention on some internal data bus in the PI triggering
>> a bus error, while 100Mbps avoids that contention. I have seen such
>> bus contention cause glitches in memory controllers in a few systems
>> over my career.
>>
>
> Thank you for that.
>
> Since the pi was always connected via the gigabit and the router
> hardware, and performed well when then routed by an external switch, it
> seems unlikely that it was the PI<=>router link that was at fault.
>
> I am leaning more towards the router buffering Internet data into large
> Gigabit Ethernet bursts that overwhelmed the Pi when it was forwarding
> to wifi. Limiting the data rate to 100Mbps allowed the Pis Ethernet to
> function well enough not to overload the wifi.
>
> It was only the Internet<=>Router<=gigabit=>Pi4<=wifi=>client that broke
>
> Without the wifi the ethernet was OK., Without the gigabit the wifi was OK.
>
> Anyway I think we both agree that it is not something that can be
> programmed around . I will test again when I get a Pi 5 and if it still
> sucks, a wifi access point is not that expensive. The Pi is also pretty
> crippled in wifi speed.
>
> I suspect the PI wifi hardware was never really designed for AP usage:
> More for client access to a Wifi station.
>
> I may try adding a wifi dongle at some point
>
It may be as simple as the cable from your router to the Pi, if it
is a different one than with the switch. Verify that you're using
a CAT6 patch cable.
I'm running a Zyxel GS-1200 switch with gigabit ports to a Pi3B+
and WLAN bridging without extra problems. The WLAN in Pi is not
completely as good a radio than a dedicated WLAN base station,
due to different antenna systems.
--
-TV
--- PyGate Linux v1.5.11
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)
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[Voltar]