MikroTik

Hi,
Today I almost started pulling my hairs off!

I have this office space in wich I put one RB951ui2hd as the main Router + Wifi wich serves 2 PCs connected via LAN ports eth 2 and 3 and I also have a second office space 30m away to wich I have a cat 5e UTP cable within walls, connected in port eth3. I want to set up a second device in the later room, a hAP Lite wich will provide wifi as well and connect 2 PCs in the same LAN.

For some reason, I can't get the hAP Lite to work. I only get a 10Mbps Full Duplex link on any ethernet port when I connect the cat5e cable wich comes from my main RB951ui2hnd.
I tried several resets and configurations and the only thing I get are some errors with link up, link down, link up, link down then settles to 10Mbps Full Duplex but it doesn't get an IP via dhcp client, I can't ping the main router, It doesn't work with static IP configuration either. It also takes a while untill the link is detected by the interface.

And here is the fun part:
If I connect the cable straight in my Dell Latitude E4310 I get a solid 100Mbps connection with Internet, full ISP speeds, IPs and all.
If I connect the cable straight in the Lenovo desktop in that office I get a 10Mbps full duplex with Internet, IPs and all.

What the..? Is the cable bad? Is the RB951ui bad..? Is there some conflict between the hAP Lite and the RB951? Is my Dell's wireless card more "ignorant" to cable issues than the Lenovo's desktop and the hAP's and that is why I get a full 100Mbps even though I find that hard to believe?

Yes I did try and crimp the cable both "straight" and "cross-over", exactly the same result!
Both hAP and RB951ui have autonegociation on, flow control off as by default.

I will attach a diagram in PDF (please rotate)

My first suggestion would be to eliminate a cable issue by temporarily moving the HAP lite into the same location as the RB951 and use a known good short cable in place of the 30M installed cable. If the HAP Lite and any downstream computer work OK in that configuration, I would assume a problem with the 30M installed cable. Get out a cable tester and test it. For all you know, someone drove a nail through the cable while hanging a photo of their kid on the wall (or any number of other possible cable issues).
If that does not help, please post your configurations.

I'd bet on a bad cable. Easy enough to try another cable between the two devices. Or basic cable tester will tell you if wires are mismatched, shorted, broken, etc.

The ethernet dialog in winbox will say what speeds and duplexes were advertised. In a working environment, it should show a few entries, 100 full, 100 half, 10 full, 10 half. I had a modem that after a brief power shutdown, it would only advertise 100 half but then use 100 full, causing excessive packet loss.

Does the cable jacket say Cat 5e, 100Mhz or better?

You could try setting both sides to use 100 Full rather than using auto-negotiation.

On the RB951's I've bought, I always avoid ether-5 as they've always given me grief with CRC errors, causing very flaky connectivity.

Ok, I've changed the cable and it works flawlessy now.

BUT, i'm still curious why my Dell Latitude's NIC did work at full 100Mbps connection and yes, it wasn't for a second or so, I did several tests for over 20 minutes and got a full 100Mbps. I'm interesed in the technical explanation really! Weird anyway!