Maximum/ ideal length of ethernet cable?

There is no ideal length of a cat 5 cable but the specification states that it should not be more than 100m (328 feet).

More info on the wiki page

The specification of 328 feet has to do entirely with collision detection in a CSMA/CD (Carrier Sense Multi Access / Collision Detection network. Basically, the length is limited by the fact that the shortest possible frame size (64 bytes) can be sent out on the wire and if a collision occurs, the sending node will still be sending that frame when it hears the collision (due to a jam signal or higher than normal amplitude). If a collision occurs during the first 64 bytes of a frame, this is a normal collision. If something is out of spec such as the cabling is too long and the collision occurs after the first 64 bytes, this is a late collision and will not be retransmitted until an upper layer of the OSI model detects that the packet did not make it to its destination. You can run longer cabling and the network will still function, but there will be issues.

The ideal length is exactly as long as you need (up to 100 meters) and no longer. Every extra 11.9 inches adds another nanosecond of extra latency.

Ideal: As short as possible, as isolated as possible.

Maximum: 100 meters without repeaters.