[toast0]

> The cables were run 15 years ago, so I expected it to be cat 5, but clearly not.

Did you check the jackets? I've got Cat5 (no e) marked cable running 10gbaseT. A lot of cable exceeds the specs on its jacket and specified wire provides enough signal to noise for the provided length in dense conduit. When you have shorter runs, without dense wiring, lesser cable can work.

[apelapan]

I can't see the cable jackets. There's just outlets in the walls. I ask building management to make a link between outlet X and Y and then they make it happen via one or more patch panels that I don't know where they are. :-)

People downthread has written, cat6 was already the goto thing 15+ years ago so perhaps that is what they put in when the office space was built. It is a well built office!