This third major section of the chapter examines routed interfaces as configured on Cisco Layer 3 switches, but with a particular goal in mind: to also discuss Layer 3 EtherChannels. Making a Layer 3 forwarding decision by comparing the destination IP address to the IP routing tableĪdding a new Ethernet data-link header/trailer to the packetįorwarding the packet, encapsulated in a new frame Stripping off the incoming frame’s Ethernet data-link header/trailer Instead, frames arriving in a routed port trigger the Layer 3 routing logic, including On a routed port, the switch does not perform Layer 2 switching logic on that frame. To do so, the switch configuration makes that port a routed port.
To perform routing, any Ethernet frames destined for any of the SVI interface MAC addresses trigger the processing of the Layer 2 switching logic, resulting in normal routing actions like stripping data-link headers, making a routing decision, and so on.Īlternately, the Layer 3 switch configuration can make a physical port act like a router interface instead of a switch interface. The switch learns the source MAC address of the frame, and the switch forwards the frame based on the destination MAC address. That is, the physical interfaces receive Ethernet frames. When Layer 3 switches use SVIs, the physical interfaces on the switches act like they always have: as Layer 2 interfaces. VLAN Routing with Layer 3 Switch Routed Ports