Cannot get over 100base T connection on one Mac in a network

[geep81]

Hello,
We have a small office network of about 15 pcs. Two are Macs in my office. I recently noticed one of the Macs only connects to the network at 100base T, but the other one connects at 1000base T. I did a lot of trouble shooting, and long story short if I swap the plugs, the Mac that is currently 100base T turns into 1000base T if I used the other plug, and the other Mac gets slower.

All the setting info in Router OS was the same, there are no differences in configuration for the two ports these Macs are on. Does anyone have some advice on how I can get both Macs to connect at 1000base T speeds?

For reference, the Mac that currently connects at 1000base T is a 2008 Mac Pro, and the Mac at 100base T is a 2013 Mac Pro.

Thank you for any help you can provide.

[dasvos]

Look at the crimping, patch panel and the wall boxes. They might have a broken connection somewhere.

[zipvault]

cables are both 5e or faster i presume.. is it cat5 / cat5e / cat6 cable

check these settings on your mac network system pref

which router is it?