100Mb limit on LAN port

The lan port on my Openwrt/Linksys WRT3200ACM is limited to 100Mb for some reason. This is what ethtool shows me on lan1:

Settings for lan1:
Supported ports: [ TP MII ]
Supported link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
Supported pause frame use: Symmetric
Supports auto-negotiation: Yes
Supported FEC modes: Not reported
Advertised link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
Advertised pause frame use: Symmetric
Advertised auto-negotiation: Yes
Advertised FEC modes: Not reported
Link partner advertised link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
Link partner advertised pause frame use: Symmetric
Link partner advertised auto-negotiation: Yes
Link partner advertised FEC modes: Not reported
Speed: 100Mb/s
Duplex: Full
Auto-negotiation: on
Port: Twisted Pair
Transceiver: external
MDI-X: Unknown
Supports Wake-on: d
Wake-on: d
Link detected: yes

Is this problem cable related? As soon as I change the config (eg. Speed 1000) the router crashes.

Any advice?
Thanks in advance!

Greetings Rob

Very possibly. Check the cable -- use a known good (and preferably short) cable. Also check the ports to make sure they're all good and free from debris without any bent pins.

Does the crash occur because of the autonegotiation in this case? That because of the cable autonegotiation fails? Or what could be the mechanism behind this?

I don't know about a crash, but a port that is unable to negotiate after being forced to a specific mode will just become inoperable.

Do you have any 100Mbps device connected?
Which version of OpenWrt are you using?

There is a 100Mpbs device connected to one of my AP's, but that should not cause my main router to throttle back? I am currently running 23.05

If it is not the cable, it might as well be problem with the lan port of the device on the other side of the link. In general it would be nice to use different combinations of devices and cables until you can pinpoint the culprit.

No, remote devices should not affect. I had a similar issue with the same router, when a 100Mbps device was connected (by cable), but it was fixed on 23.05; but this is not your case.

I'll do some testing with an other cable connected to my laptop directly to see wether this solves the issue. If this is the case then I'll know it's a cable issue or not...

update: cable issue. So, I'll need to replace the cable :confused:

Thanks all for your replies!

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