3Com SuperStack 4, Configuration Manual

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182 C
HAPTER
7: M
ULTICAST
P
ROTOCOL
Configuring the IGMP Version
Perform the following configuration in Interface View.
By default, IGMP Version 2 is used.
All routers on a subnet must support the same version of IGMP. After detecting
the presence of IGMP Version 1 system, a router cannot automatically switch to
Version 1.
Configuring the Interval for Querying IGMP Packets
The router finds out which multicast groups on its connected network segment
have members by sending IGMP query messages periodically. Upon the reception
of a response message, the router refreshes the membership information of the
corresponding multicast group.
Perform the following configurations in Interface View.l
When there are multiple multicast routers on a network segment, the querier is
responsible for sending IGMP query messages to all the hosts on the LAN.
By default, the interval is 60 seconds.
Configuring the Interval and the Number of IGMP Query Packets
On a shared network, the query router (querier) maintains IGMP membership on
the interface. When an IGMP querier receives an IGMP Leave Group message from
a host, the last member query interval can be specified for Group-Specific Queries.
1 The host sends the IGMP Leave message.
2 Upon receiving the message, the IGMP querier sends the designated group IGMP
query message for the specified number of times (defined by the
robust_value
in
igmp robust-count
, with the default value as 1 second) and at a time interval
(defined by the
seconds
in
igmp lastmember-queryinterval
, with the default
value as 2).
3 When other hosts receive the message from the IGMP querier and are interested
in this group, they return the IGMP Membership Report message within the
defined maximum response time.
4 If the IGMP querier receives the report messges from other hosts within the period
equal to
robust-value
×
seconds , it continues membership maintenance for this
group.
Table 190 Selecting the IGMP version
Operation Command
Select the IGMP version that the router uses
igmp version { 1 | 2 }
Restore the default setting
undo igmp version
Table 191 Configuring query interval
Operation Command
Configure query interval
igmp timer query
seconds
Restore the default query interval
undo igmp timer query