OpenWRT
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Trouble Shooting
Wrong Link Speed
I had a problem with link-speed between Docsis-modem in front and a OpenWRT-Router. OpenWRT displayed only 10Base-T (10Mbit/s).
It turns out that (against my expections/assumptions) OpenWRT did not support Auto MDI-X (Wikipedia EN: Medium Dependent Interface).
1 # ethtool eth0
2 Settings for eth0:
3 Supported ports: [ ]
4 Supported link modes: 1000baseT/Full
5 Supported pause frame use: No
6 Supports auto-negotiation: No
7 Supported FEC modes: Not reported
8 Advertised link modes: 1000baseT/Full
9 Advertised pause frame use: No
10 Advertised auto-negotiation: No
11 Advertised FEC modes: Not reported
12 Speed: 1000Mb/s
13 Duplex: Full
14 Port: MII
15 PHYAD: 0
16 Transceiver: external
17 Auto-negotiation: on
18 Current message level: 0x000000ff (255)
19 drv probe link timer ifdown ifup rx_err tx_err
20 Link detected: yes
So all you need to change to achieve the intended Link-Speed is to use
- a cross-over cable or
even simpler a (Amazon:) cross-over adapter, which turns some pins of any RJ-45 plug.