Cisco Catalyst 4500 Series Software Configuration Guide

38-9
Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.xE and IOS 15.2(5)Ex
Chapter 38 Configuring IP Multicast
About IP Multicast
Hardware and Software Forwarding
The Integrated Switching Engine forwards the majority of packets in hardware at very high rates of
speed. The CPU subsystem forwards exception packets in software. Statistical reports should show that
the Integrated Switching Engine is forwarding the vast majority of packets in hardware.
Figure 38-5 shows a logical view of the hardware and software forwarding components.
Figure 38-5 Hardware and Software Forwarding Components
In the normal mode of operation, the Integrated Switching Engine performs inter-VLAN routing in
hardware. The CPU subsystem supports generic routing encapsulation (GRE) tunnels for forwarding in
software.
Replication is a particular type of forwarding where, instead of sending out one copy of the packet, the
packet is replicated and multiple copies of the packet are sent out. At Layer 3, replication occurs only
for multicast packets; unicast packets are never replicated to multiple Layer 3 interfaces. In IP
multicasting, for each incoming IP multicast packet that is received, many replicas of the packet are sent
out.
IP multicast packets can be transmitted on the following types of routes:
• Hardware routes
• Software routes
• Partial routes
Hardware routes occur when the Integrated Switching Engine hardware forwards all replicas of a packet.
Software routes occur when the CPU subsystem software forwards all replicas of a packet. Partial routes
occur when the Integrated Switching Engine forwards some of the replicas in hardware and the CPU
subsystem forwards some of the replicas in software.
Partial Routes
Note The conditions listed below cause the replicas to be forwarded by the CPU subsystem software, but the
performance of the replicas that are forwarded in hardware is not affected.
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