The official standards for Cat5 / Cat6 depict a cable run no longer than 90 meters from device to device.
If you require a cable run longer than 90 meters you will need to add an active hardware device such as a switch, hub or router in to your network topology.
Another alternative for exceptionally long cable runs is moving over to a fibre cable and connection. Most higher end, larger port switches have SFP ports use for this purpose.
For more information on SFP please click here