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ngoonee

Forum Fellow

From: Between Thailand and Singapore

Registered: 2009-03-17

Posts: 7,358

DHCP not working with a specific USB Type C multi-port adapter

I've got a laptop without an ethernet port (thin and light etc. etc.), and so have have been working on wireless without issues. I use NetworkManager to manage it.

I recently purchased a multi-port (ethernet, USB2.0, and HDMI) adapter for use when I'm at my office table. The ethernet component seems to function partially:-

1. Plugging in the adapter brings up an ethernet device (enp0s20f0u2u3) properly, which is seen by NetworkManager.
2. Plugging in an ethernet cable to the adapter results in NetworkManager trying to make the connection, this never completes.

I disabled NetworkManager to try to see what was going on, it ended up being that DHCP would never return, whether using dhcpcd or dhclient. It would just time out or retry repeatedly. This was tested by running dhcpcd/dhclient standalone without NetworkManager being enabled, of course.

Setting a fixed IP address works mostly fine (though I get many more lost packets/disconnects than I'd expect for a wired connection, this is not the cable because it's taken from another working Linux machine specifically to rule out hardware problems. In particular this means I need to restart cntlm once in a while.

I'm suspecting a hardware fault in the adapter but can't say for sure since a fixed IP address allows me to connect. Anyone more knowledgeable in specs/hardware have any advise on things I could try?

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Allan-Volunteer on the (topic being discussed) mailn lists. You never get the people who matters attention on the forums.
jasonwryan-Installing Arch is a measure of your literacy. Maintaining Arch is a measure of your diligence. Contributing to Arch is a measure of your competence.
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Trilby

Inspector Parrot

Registered: 2011-11-29

Posts: 30,332

Website

Re: DHCP not working with a specific USB Type C multi-port adapter

Appologies if this is obvious - but are you only using the ethernet part of the adapter with the usb2 and HDMI not connected to anything?  Ideally it shouldn't matter, but perhaps there'd be potential interference from the other channels if they are also in use.

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"UNIX is simple and coherent" - Dennis Ritchie; "GNU's Not Unix" - Richard Stallman

ngoonee

Forum Fellow

From: Between Thailand and Singapore

Registered: 2009-03-17

Posts: 7,358

Re: DHCP not working with a specific USB Type C multi-port adapter

Appologies if this is obvious - but are you only using the ethernet part of the adapter with the usb2 and HDMI not connected to anything?  Ideally it shouldn't matter, but perhaps there'd be potential interference from the other channels if they are also in use.

Yes, nothing else is connected (including the power supply of the laptop), only the adapter and the LAN cable. I've seen problems related to interference (in particular power supply interference) before as well.

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Allan-Volunteer on the (topic being discussed) mailn lists. You never get the people who matters attention on the forums.
jasonwryan-Installing Arch is a measure of your literacy. Maintaining Arch is a measure of your diligence. Contributing to Arch is a measure of your competence.
Griemak-Bleeding edge, not bleeding flat. Edge denotes falls will occur from time to time. Bring your own parachute.

ngoonee

Forum Fellow

From: Between Thailand and Singapore

Registered: 2009-03-17

Posts: 7,358

Re: DHCP not working with a specific USB Type C multi-port adapter

Curiouser and curiouser, DHCP worked well on another network (one where I control the router). This is disturbing....

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Allan-Volunteer on the (topic being discussed) mailn lists. You never get the people who matters attention on the forums.
jasonwryan-Installing Arch is a measure of your literacy. Maintaining Arch is a measure of your diligence. Contributing to Arch is a measure of your competence.
Griemak-Bleeding edge, not bleeding flat. Edge denotes falls will occur from time to time. Bring your own parachute.

progandy

Member

Registered: 2012-05-17

Posts: 5,280

Re: DHCP not working with a specific USB Type C multi-port adapter

That is really strange. Did you try and disable ECN as well as check for duplex mismatch?

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ngoonee

Forum Fellow

From: Between Thailand and Singapore

Registered: 2009-03-17

Posts: 7,358

Re: DHCP not working with a specific USB Type C multi-port adapter

Thanks for the reply, been a long weekend here so I've not been back to the office till today. Will try this out soonish.

EDIT: Disabling ECN didn't help. Also auto-negotiation is set (and works on a windows computer). Unlikely to be a software issue given the adapter also shows similar behaviour in Windows (only able to use fixed IP, no DHCP granted).

Last edited by ngoonee (2018-09-12 08:48:29)

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Allan-Volunteer on the (topic being discussed) mailn lists. You never get the people who matters attention on the forums.
jasonwryan-Installing Arch is a measure of your literacy. Maintaining Arch is a measure of your diligence. Contributing to Arch is a measure of your competence.
Griemak-Bleeding edge, not bleeding flat. Edge denotes falls will occur from time to time. Bring your own parachute.