Configure the optical port of a Layer 3 switch

An optical port on a Layer 3 switch can be used as a routed interface by connecting the fiber module and configuring it with an IP address for Layer 3 routing.

Physical Connection

Insert the SFP/SFP+ module into the optical port of the switch. Ensure the module type matches the fiber cable (single-mode or multi-mode) and the distance requirements. Connect the fiber optic cable to the module, observing proper polarity (TX to RX and RX to TX) to ensure signal integrity.

Verify link status using the switch CLI or management interface to confirm the port is operational. Configuring the Optical Port as a Layer 3 InterfaceOptical ports on Layer 3 switches function like any other physical interface and can be configured as routed ports: Enter interface configuration mode for the optical port: CodeCopyinterface TenGigabitEthernet1/1/1 Replace with the actual port identifier. Convert the port to a routed interface (disable Layer 2 switching): CodeCopyno switchport This allows the port to operate at Layer 3, forwarding IP packets instead of Ethernet frames only.

Assign an IP address to the port: CodeCopyip address 192. 168. 1.

1 255. 255. 255.

0 This IP will serve as the gateway for devices on the connected subnet. Enable routing protocols if needed: For static routing, configure routes pointing to the next-hop IP. For dynamic routing, enable protocols like OSPF or EIGRP on the interface.

Verify configuration: CodeCopyshow ip interface brief The optical port should appear as a Layer 3 interface with the assigned IP and an "up/up" status.

Optional Configurations

Subinterfaces: If the optical link carries multiple VLANs, create subinterfaces with unique IP addresses for inter-VLAN routing. Layer 3 EtherChannel: Aggregate multiple optical ports into a single routed port channel for higher bandwidth and redundancy.

SV

I vs Routed Port: Use a routed port for a single physical connection to a subnet. Use an SVI if multiple ports connect to the same VLAN internally.

Summary

Using an optical port on a Layer 3 switch involves physically connecting the fiber module, converting the port to a routed interface, and assigning an IP address for Layer 3 routing. This enables the optical port to forward IP traffic, participate in routing protocols, and interconnect networks efficiently, just like a copper routed port.