 | Copyright © 2008, Juniper Networks, Inc. All rights reserved. Trademark Notice. | |
A J-series device usually learns unicast MAC addresses by checking the source address field of the frames it receives. However, a multicast MAC address can never be the source address for a packet. As a result, the switch floods multicast traffic on the VLAN, consuming significant amounts of bandwidth.
IGMP snooping regulates multicast traffic on a VLAN to avoid flooding. When IGMP snooping is enabled, the switch intercepts IGMP packets and uses the content of the packets to build a multicast cache table. The cache table is a database of multicast groups and their corresponding member ports. The cache table is then used to regulate multicast traffic on the VLAN.
When the router receives multicast packets, it uses the cache table to selectively forward the packets only to the ports that are members of the destination multicast group.
| Copyright © 2008, Juniper Networks, Inc. All rights reserved. Trademark Notice. | |