The specified maximum distance for a cat5 segment is 100m.
This includes 90m of structured wiring, and 10m of patch cables. The 100m segment will support the full bandwidth.
People have successfully exceeded 100m with full duplex links between switches, but it is not recommended as a standard practice.
If you are running a link between buildings, it is recommended that you run fiber to eliminate any possible differential in ground voltages between endpoints.
