OM4 (Optical Multimode 4) is a type of multimode optical fiber cable that is commonly used in data center and high-speed networking applications. The distance that a 25G Ethernet link can cover using OM4 fiber depends on several factors, including the transceiver technology, the quality of the fiber installation, and the specific requirements of the networking equipment.

For 25G Ethernet over OM4 multimode fiber, the typical reach is up to 100 meters. This means that under standard conditions and using appropriate transceivers, you can achieve reliable data transmission at 25 gigabits per second over a distance of 100 meters.

It's important to note that the actual achievable distance may vary based on factors such as the quality of the fiber optic cable, the connectors used, and the specific transceivers employed. Additionally, signal integrity and link performance can be influenced by factors like bends, splices, and environmental conditions.

Always refer to the specifications provided by the equipment manufacturers and the transceiver datasheets for accurate information on the supported distances for your specific setup.