Cisco Catalyst 2960 Series User Manual

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 that includes the port numbers connected to Host 1 and to the router.
Table 13: IGMP Snooping Forwarding Table
PortsType of PacketDestination Address
1, 2IGMP224.1.2.3
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.
If another host (for example, Host 4) sends an unsolicited IGMP join message for the same group, the CPU
receives that message and adds the port number of Host 4 to the forwarding table. Because the forwarding
table directs IGMP messages only to the CPU, the message is not flooded to other ports on the switch. Any
known multicast traffic is forwarded to the group and not to the CPU.
Figure 5: Second Host Joining a Multicast Group
Table 14: Updated IGMP Snooping Forwarding Table
PortsType of PacketDestination Address
1, 2, 5IGMP224.1.2.3
Related Topics
Configuring a Host Statically to Join a Group , on page 133
Consolidated Platform Configuration Guide, Cisco IOS Release 15.2(4)E (Catalyst 2960-X Switches)
120
Information About IGMP Snooping and MVR

Cisco Catalyst 2960 Series Specifications

General

Layer	Layer 2
Power over Ethernet (PoE)	Available on some models
RAM	128 MB
Flash Memory	32 MB
MAC Address Table Size	8000
Operating Temperature	0°C to 45°C (32 to 113°F)
Ports	24 or 48 x 10/100/1000