Install guide

IP Multicasting 17
To specify the type of log messages and SNMP traps that the switch generates,
use the command:
set pim log={none|status|error|all}
[trap={none|status|error|all}]
To display the specified options, use the command:
show pim debug
Internet Group Management Protocol (IGMP)
IGMP is a protocol used between hosts and multicast routers and switches on a
single physical network to establish hosts’ membership in particular multicast
groups. Multicast routers use this information, in conjunction with a multicast
routing protocol, to support IP multicast forwarding across the Internet.
The switch supports Internet Group Management Protocol version 2
(IGMPv2), defined in RFC 2236, Internet group Management Protocol, version 2. It
can also detect and interoperate with hosts and other designated routers
(sometimes called querier routers) running IGMP version 1.
When IGMP is enabled on the switch, and on particular interfaces, it sends out
IGMP queries on all IGMP interfaces. If it receives an IGMP message from a
router with a lower IP address on an interface, it knows that another switch is
acting as the IGMP designated router for that subnetwork. If it receives no
IGMP messages with a lower IP address, it takes the role of designated switch
for that subnetwork. If it is the designated switch, it continues to send out
general IGMP Host Membership Queries regularly on this interface.
When an IP host hears a general IGMP Host Membership Query from the
switch, it sends an IGMP Host Membership Report back to the switch. All the
IGMP routers on the subnetwork put an entry into their local group database, so
that the switches know which interfaces to send packets for this multicast
group out of. These entries are updated regularly, as long as the interface has a
member of the multicast group connected to it. As hosts join and leave
multicast groups dynamically, the switch keeps a list of group memberships for
each of its primary interfaces. In the case of multihomed interfaces, the primary
interface is the first interface to be configured.
When an IP host stops belonging to a multicast group, it sends an IGMP Leave
message to the switch. The switch then sends one or more group-specific IGMP
membership queries, and any other IP hosts belonging to the same multicast
group reply with a Host Membership Report. IGMP then knows whether there
are still any members of this multicast group connected to the interface.