The Cisco 4000 series ISRs (Integrated Service Routers) are designed to greatly improve enterprise branch networks routing and network services. Because of their application-aware networking features and a wide array of voice, security and application expansion licenses, the ISR4000 series can be custom fitted to meet the needs of a wide variety of enterprise networks.
The Cisco ISR4331/K9 ships with 3 gigabit Ethernet ports, 2 network interface module slots and 1 service module slot. These 3 ports include one dedicated RJ-45 port, one dedicated SFP port, and one dual mode RJ-45/SFP port. This dual mode port can only be used as either copper of SFP at any given time, not both. Because of this, the ISR 4331 has a maximum of 3 usable interfaces, even though 4 are physically present on the unit