Cisco Systems WS-X5104 Network Interface Module

The Cisco WS-X5104 Network Interface Module is a four-port FDDI (Fiber Distributed Data Interface) interface card designed for Cisco Catalyst 5000 series switches, expanding fiber-based backbone connectivity within enterprise networks and enabling redundant, high-bandwidth links across campus, data-center, or metropolitan-scale backbones. Each port provides an independent FDDI channel over single-mode fiber, supporting reliable long-distance links and improved resistance to electrical noise compared with copper-based interfaces, making it suitable for core or distribution-layer deployments where FDDI remains in use. As a legacy Catalyst module, it is installed in a compatible Catalyst 5000 chassis with the appropriate supervisor module and backplane to carry FDDI traffic, and is commonly used to create FDDI backbone rings or connect multiple switches in a fiber-based fabric. The WS-X5104 sits among Cisco's WS-X Catalyst 5000 family and represents the older generation of high-availability fiber options, frequently encountered in retrofit projects and networks maintaining legacy FDDI infrastructure.