"no link detected" for ethernet connection to cable modem

[mih]

Hi,

I just received my first B3. I was not able to get a connection between the B3 and my cable modem working. When I plug the cable in I get no link lights at either end (B3 and modem). I obviously tried different cables, and additionally the B3 is simply replacing a similar machine in the same setup -- so it should work. There was a hint in the forum that loop-connecting the WAN and LAN port should give GB-link-light - which it does. A little more research revealed that I can only get the B3 and the modem to acknowledge a connection when I force the B3's WAN port into 10baseT mode (the modem actually has a 100baseT port). But even in this case the B3 fails to obtain an IP from my ISP. The modem itself is transparent (e.g. there is nothing to configure).
The modem is a Thomson THG520.

Has anyone seen anything like this before?

I can connect to the B3's WAN port when attaching any other device with a Gigabit port, so it doesn't seem to be entirely broken.

Thanks in advance,

Michael

[Binkem]

Sorry I cannot be clearer, buy you might have to adjust the Ethernet settings with ethtool. You can use it to force a certain speed and set autoneg on or off.

Martijn

[Cheeseboy]

Hi Michael,

I jut had a quick look at the manual for the Thomson THG520.
It seems to have two (!) different reset buttons...

I don't mean to sound condescending or anything, but have you tried them? And the diagnostics Windows software that connects to the device over USB?

A simpler thing to try might be to bring your B3 unit to a friend's house and try it there.
If it still fails with the default settings, just contact Excito support and they will probably send you a new one


Cheers,

Stinkyfeet

[mih]

Sorry I cannot be clearer, buy you might have to adjust the Ethernet settings with ethtool. You can use it to force a certain speed and set autoneg on or off.

Martijn

Yes, I did use ethtool the try tne settings that I mentioned in my original post. But as I said, it did not lead to a solution.

Michael

[mih]

Hi Michael,

I jut had a quick look at the manual for the Thomson THG520.
It seems to have two (!) different reset buttons...

I don't mean to sound condescending or anything, but have you tried them? And the diagnostics Windows software that connects to the device over USB?

A simpler thing to try might be to bring your B3 unit to a friend's house and try it there.
If it still fails with the default settings, just contact Excito support and they will probably send you a new one


Stinkyfeet

I did reset the modem quite a few times in this process, no luck. I do not have a windows box that I could connect to the modem. But I see no real need to investigate problems on the modem end. I connected five different devices from five different vendors -- they all work just fine. The modem has been working reliably for many years now. I contacted my ISP and ask for known compatibility issues, but they find this model to be fairly robust. I could get a different model for 150 EUR, but again, it is working just fine -- except for the B3.

I wrote an email to the support and asked for advice.

Thanks for your thoughts!

Michael

[johannes]

@Michael, it is known that some modems have trouble getting a link connection to the B3. Both products get link together with other devices, but apparently some combination of devices does not work well. (This is not a totally unknown problems, for instance some netgear switches cannot get link together with other identical switches, but works with other devices)

Possible workarounds:

1) fiddle with ethtool as suggested to try other speeds / duplex etc, might work
2) use another ethernet cable
3) exchange your ADSL modem
4) put a switch in between the B3 and your modem

Really sorry for the problems. If you suspect issues with the B3 let us know and we'll replace it, but my guess is that it will get link if you connect it to other equipment.

[Gordon]

If the issue is with autosensing speed and duplex, you might also try to use a cable that does not have the two brown wires connected. You can either make that cable yourself or dig into an existing cable to cut them halfway. Without these two wires no device will ever accept gigabyte transfer and should in this case fall back to a mode that both devices can work with.

edit:
Come to think about it.... Although this being a modem the LAN connector may still be designed to be tied to a switch (or hub) rather than straight to a computer. If this is the case than besides leaving the autosense (brown) wires out you may have to crosswire green (receive) and orange (transmit). Actually crosswiring might be sufficient and by leaving the brown wires in you could still use this cable for other (gigabit) appliances later on. If you can't do your own cables, you could also do this crossing inside a RJ45 wall connector.