Cisco 3750G - Catalyst Integrated Wireless LAN Controller User Manual

24-4
Catalyst 3750 Switch Software Configuration Guide
OL-8550-02
Chapter 24 Configuring IGMP Snooping and MVR
Understanding IGMP Snooping
Figure 24-1 Initial IGMP Join Message
Router A sends a general query to the switch, which forwards the query to ports 2 through 5, which are
all members of the same VLAN. Host 1 wants to join multicast group 224.1.2.3 and multicasts an IGMP
membership report (IGMP join message) to the group. The switch CPU uses the information in the IGMP
report to set up a forwarding-table entry, as shown in Table 24-1, that includes the port numbers
connected to Host 1 and the router.
The switch hardware can distinguish IGMP information packets from other packets for the multicast
group. The information in the table tells the switching engine to send frames addressed to the 224.1.2.3
multicast IP address that are not IGMP packets to the router and to the host that has joined the group.
Forwarding
table
CPU
Host 1 Host 2 Host 3 Host 4
Router A
IGMP report 224.1.2.3
VLAN
PFC
1
0
2345
45750
Table 24-1 IGMP Snooping Forwarding Table
Destination Address Type of Packet Ports
224.1.2.3 IGMP 1, 2

Cisco 3750G - Catalyst Integrated Wireless LAN Controller Specifications

General

Switching Capacity	32 Gbps
RAM	128 MB
Flash Memory	32 MB
Power Device	Internal power supply
Ports	48 x 10/100/1000 + 4 x SFP
Performance	38.7 Mpps
Wireless LAN Controller Capacity	50
Stacking	Yes
Features	VLAN support, QoS
Compliant Standards	IEEE 802.3, IEEE 802.3u, IEEE 802.3ab, IEEE 802.3z
Operating Humidity	10% to 85% non-condensing
Power over Ethernet (PoE)	Yes (optional)