Cisco Catalyst 4500 Series Administration Guide

35-5
Software Configuration Guide—Release IOS XE 3.5.0E and IOS 15.2(1)E
OL_28731-01
Chapter 35 Configuring Cisco Express Forwarding
Catalyst 4500 Series Switch Implementation of CEF
Figure 35-2 Hardware and Software Switching Components
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
Hardware switching is the normal operation for Supervisor Engine III and Supervisor Engine IV.
Software Switching
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
Note 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 for routing
• 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

Cisco Catalyst 4500 Series Specifications

General

Series	Catalyst 4500 Series
Category	Switch
Layer Support	Layer 2, Layer 3
Form Factor	Modular chassis
Stackable	No
Chassis Slots	3, 6, 7, 10
Power Supply Options	AC, DC
Redundancy	Power supply, Supervisor engine
Network Management	Cisco IOS Software CLI, SNMP, Cisco Prime Infrastructure
Features	Security, QoS
Port Density	Up to 384 ports per chassis
Security Features	802.1X, ACLs, DHCP Snooping, Dynamic ARP Inspection, IP Source Guard
Supervisor Engine	8-E