As I posted here a couple of weeks ago, I was looking for some solution to network the ground and first floors of my house. I've given up on the wireless solution -- too expensive right now -- so I went with running cable down the outside of the house.

Diagram:

Switch <- cat5 -> Wall |- cat5 -| Wall <- cat5 -> hub (uplink) <- cat5 -> empeg

I cabled both ends according to the diagram inside the wall plate[1].

This is almost working correctly. I get link lights on the switch upstairs and the hub downstairs. I don't, however, seem to be getting any packets to make their way downstairs -- I'm seeing DHCPREQUEST packets on the server upstairs, but the DHCPOFFER packets don't seem to be making it back downstairs.

The other oddity is that I get a lot of collisions if I plug the cable into the uplink port on the downstairs hub, which I wasn't expecting. If I plug it into a normal port, I get no collisions. I get link in both cases, it seems.

The rest of the patch cables are fine -- I tested them separately [2], and the hub and switch have talked to eachother in the past.

So, questions:

1. Which pairs are actually used on the cable, and for what? I'm considering swapping one of the unused pairs over, in case there's a break in the cable somewhere.
2. If I want the uplink port to work, which pairs do I need to swap on the back of the wallplate?

Advice?

[1] except that the wall plate diagram showed blue-and-white and white-and-blue (etc.) on the terminals, which confused the issue slightly.
[2] And besides, I'm a UTP crimping god -- I've not done a single bad crimp yet (touch wood-effect desktop).