Cisco Systems WSC4500X16SFP Manual De Usuario

The Integrated Switching Engine performs inter-VLAN routing in hardware. The CPU subsystem 
software supports Layer 3 interfaces to VLANs that use Subnetwork Access Protocol (SNAP) 
encapsulation. The CPU subsystem software also supports generic routing encapsulation (GRE) tunnel. 

Hardware switching is the normal operation for the Supervisor Engine III and Supervisor Engine IV.

Software switching occurs when traffic cannot be processed in hardware. The following types of 
exception packets are processed in software at a much slower rate:

Packets that use IP header options 

Packets that use TCP header options are switched in hardware because they do not affect the 
forwarding decision.

Packets that have an expiring IP time-to-live (TTL) counter

Packets that are forwarded to a tunnel interface 

Packets that arrive with non-supported encapsulation types

Packets that are routed to an interface with non-supported encapsulation types

Packets that exceed the MTU of an output interface and must be fragmented

Packets that require an IGMP redirect to be routed

802.3 Ethernet packets

Integrated Switching Engine

CPU Subsystem

GRE

tunnel

L3 physical
interface

Router

L3 interfaces

L2 switchports 

68127

VLAN1

Gig 1/1

VLAN2

GRE

tunnel