System information

9-92
Configuring Advanced Features
Multimedia Traffic Control with IP Multicast (IGMP)
Configuring Advanced
Features
Enabling IGMP allows the ports to detect IGMP queries and report packets
and manage IP multicast traffic through the switch. If no other querier is
detected, the switch will then also function as the querier. (If you need to
disable the querier feature, you can do so through the IGMP configuration
MIB. Refer to “Changing the Querier Configuration Setting” on page 9-97.)
Note IGMP configuration on the Switch 2512/2524 operates at the VLAN context
level. If you are not using VLANs, then configure IGMP in VLAN 1 (the default
VLAN) context. IGMP requires an IP address and subnet mask for any VLAN
used for IGMP traffic. If the switch relies on DHCP or Bootp to acquire an IP
address, ensure that an IP addressing has been assigned to the appropriate
VLANs by using
show ip or by viewing the menu interface “Management
Address Information” screen (page 10-6).
In order for IGMP service to take effect, an IP address must be configured and
active on the VLAN in which you want IGMP to operate. If the only VLAN on
the switch is the default VLAN (VLAN ID, or VID, of “1”), then you must
configure an IP address for VLAN 1. If multiple VLANs are configured, you
must configure an IP address for the VLAN(s) in which you want to implement
IGMP. Refer to “IP Configuration” on page 5-3.
IGMP Operating Features
In the factory default configuration, IGMP is disabled. If multiple VLANs are
not configured, you must configure IGMP on the default VLAN
(DEFAULT_VLAN; VID = 1). If multiple VLANs are configured, you must
configure IGMP on a per-VLAN basis. When you use either the CLI or the web
browser interface to enable IGMP on the switch or a VLAN, the switch
forwards IGMP traffic only to ports belonging to multicast groups. Using the
console enables these additional options:
■ Forward with High Priority. Disabling this parameter (the default)
causes the switch or VLAN to process IP multicast traffic, along with other
traffic, in the order received (normal priority). Enabling this parameter
causes the switch or VLAN to give a higher priority to IP multicast traffic
than to other traffic.
■ Auto/Blocked/Forward: You can use the console to configure individual
ports to any of the following states:
• Auto (the default): Causes the switch to interpret IGMP packets and
to filter IP multicast traffic based on the IGMP packet information for
ports belonging to a multicast group. This means that IGMP traffic
will be forwarded on a specific port only if an IGMP host or multicast
router is connected to the port.