So, the situation is like this:

I'm renting an apartment in a large house and I'm sharing internet with the landlord who lives downstairs.

The internet is (in my best guess) optical 20/20Mbit. I don't know how it's all wired in his flat (haven't been there / seen it).

Anyway, in my flat comes a cable which seems to be connected directly to the optic to ethernet router (and the password is the default one, so I have access, he he). There was a switch connected to that and to wires that go around the flat, and the wiring is terrible. It's even mixing phone and ethernet, and from what I see some cables are even interconnected!?

Anyways, this cable that comes to my flat is very short. I can barely connect my computer on it, but if I do, I seem to get decent speed / performance. Not great, but decent.

If, however, I connect switch to it (tried 2 different switches and a wifi switch) it's all blinking but I can't even connect to 192.168.1.1 (the router). DHCP fails, ping is losing 80-100% of replies.

So I connected this cable directly to the other cable which goes to my work room, with a connector that has two female jacks and no electronics. Now when I connect my computer in my room, again, the performance is decent.

When I connect WRT54GL (with tomato, DHCP disabled) to it and I plug a cable in this WRT and to my computer... the performance is gone. Download seems okay on Speedtest, but upload is .2Mbps and it's connecting forever.

So what kind cable troll am I having here? Any ideas?