I have been buying a few more GLiNet devices again recently and have noticed some strange behaviour with ethernet cable detection when running as an access point. Recently Ive added an gl-sft1200 (Opal) to my collection and this is what Ive been testing with.
If the ethernet cable is only 2 pair (e.g. fast ethernet cables but not full gigabit with 4 pair) then the cable is not detected by the router. Ive tested several cables and setups but this does appear to be the problem.
Is there any way to override this logic? Since some of my cable runs have two devices on the end of them (e.g. 2 pairs for one device and 2 pairs for another).
I appreciate that, however I regularly see patch cables with only 2 pairs wired, and if a device is capable of supporting fast ethernet then why would it not do it with 2 pairs?
it is out of spec, but I had a look to it myself on google since I did not learned this on school, I only knew about straight cables and cross over cables.
But to awnser:
Only one pair can have 1gb, the other pair 100M this is probably due to the amount of coring.
One has the core wire for power, the other jacket has not and is weaker.
Atleast that is what my assumption is when looking to this picture here:
Basically it splits as a splitter but negotiate different per jacket.
I don't know the technical side but since it is out of spec I would think it has a chance of negotiation flapping... but not sure, if my theory holds true you need to set the negotiation on 100M on the router with ethtool, like ethtool -s lan1 speed 100 full duplex autoneg off everytime the router restarts, if it was connected on lan1.
A constant confusion between 1gb and 100M will overwhelm the port and shut it down, any misaligned handshakes with negotiation also shutdown, by picking the lowest this will not happen anymore.
I would just go with a normal 4 pair cable and a network switch for expanding.
Yes, thats the sort of thing I meant, and thats how I confirmed it was to do with 2 pair v.s. 4 pair cables causing detection problems. Some cheap (flat) ethernet cables don’t seem to bother with 4 pairs, especially if the device is only capable of running at 100Mbps.
It seems like the GLiNet firmware doesnt detect a cable at all, if it only has 2 pairs and hence is limited by 100Mbps connection. I will investigate whether I can force the negotiation though using your method, thank you!
