Connectivity Guide
• OS10 uses version 3 as the default IGMP version. Version 3 is backwards compatible with versions 1 and 2.
Important notes
• OS10 systems cannot serve as an IGMP host or an IGMP version 1 querier.
• OS10 automatically enables IGMP on interfaces where you enable PIM sparse mode.
Supported IGMP versions
IGMP has three versions. Version 3 obsoletes and is backwards-compatible with version 2; version 2 obsoletes version 1.
OS10 supports the following IGMP versions:
• Router—IGMP versions 2 and 3. The default is version 3.
• Host—IGMP versions 1, 2, and 3.
In IGMP version 2, the host expresses interest in a particular group membership (*, G). In IGMP version 3, the host expresses interest in a
particular group membership, and species the source from which it wants the multicast trac (S, G).
Query interval
The IGMP querier periodically sends a general query to discover which multicast groups are active. A group must have at least one host to
be active. By default, the periodic query messages are sent every 60 seconds. You can congure this value using the ip igmp query-
interval command.
To congure a query interval:
OS10# configure terminal
OS10# interface vlan120
OS10(conf-if-vl-120)# ip igmp query-interval 60
Last member query interval
When the IGMP querier receives a leave message, it sends a group-specic query message to ensure if any other host in the network is
interested in the multicast ow. By default, the group-specic query messages are sent every 1000 milliseconds. You can congure this
value using the ip igmp last-member-query-interval command.
To congure last member query interval:
OS10# configure terminal
OS10# interface vlan120
OS10(conf-if-vl-120)# ip igmp last-member-query-interval 200
Maximum response time
The maximum response time is the amount of time that the querier waits for a response to a query before taking action.
When a host receives a query, it does not respond immediately, but rather starts a delay timer. The delay time is set to a random value
between 0 and the maximum response time. The host sends a response when the timer expires; in IGMP version 2, if another host
responds before the timer expires, the timer nullies, and no response is sent.
Multicast
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