Configuring IGMP Settings for an Interface

When you start IGMP on an interface, it operates with the default settings. You can, however, modify:

• The method that the router uses to remove hosts from multicast groups (IGMPv2 and IGMPv3 interfaces only)
• The query time interval for the querier sends group membership messages
• The time that a non-querier waits for queries from the current querier before sending query messages to assume responsibility of querier
• The time that a new querier waits before sending query messages after it assumes responsibility from another querier
• The time that a host can take to reply to a query (maximum response time)
• The number of times that the router sends each IGMP message from this interface

ip igmp immediate-leave

• Use to specify that, when the router receives a leave group membership message from a host associated with this interface, the router immediately removes that host from the multicast group.

  Caution: Issue this command only on IGMPv2 and IGMPv3 interfaces to which one IGMP host is connected. If more than one IGMP host is connected to a LAN through the same interface, and one host sends a leave group message, the router removes all hosts on the interface from the multicast group. The router loses contact with the hosts that must remain in the multicast group until they send join requests in response to the router's next general group membership query.

• Use the IGMP-Immediate-Leave RADIUS attribute (VSA 26-97) in RADIUS Access-Accept messages as an alternative method of configuring this value. The RADIUS setting takes precedence over a CLI setting.
• Example

  host1:boston(config-if)#ip igmp immediate-leave

• Use the no version to restore the default behavior, in which the router removes a host from a multicast group if that host does not return a group membership report within a certain length of time after receiving a group membership query from the router.
• See ip igmp immediate-leave.

ip igmp last-member-query-interval

• Use to specify the last-member-query-interval value, in the range 1–255 tenths of a second. When the router receives an IGMPv2 leave message or an IGMPv3 state change report, it sends out a query and expects a response within the time specified by this value.
• Using a lower value enables members to leave groups more quickly.
• Example

  host1:boston(config-if)#ip igmp last-member-query-interval 90

• Use the no version to restore the default, 10-tenths of a second (1 second).
• See ip igmp last-member-query-interval.

ip igmp querier-timeout

• Use to set the time, in the range 1–400 seconds, that the interface waits for queries from the current querier before sending query messages to assume responsibility of querier.
• Example

  host1:boston(config-if)#ip igmp querier-timeout 200

• Use the no version to set the time to the default, twice the query interval.
• See ip igmp querier-timeout.

ip igmp query-interval

• Use to specify how often, in the range 1–300 seconds, the interface sends group membership queries.
• Use the IGMP-Query-Interval RADIUS attribute (VSA 26-95) in RADIUS Access-Accept messages as an alternative method of configuring this value. The RADIUS setting takes precedence over a CLI setting.
• Example

  host1:boston(config-if)#ip igmp query-interval 100

• Use the no version to set the polling interval to the default, 125 seconds.
• See ip igmp query-interval.

ip igmp query-max-response-time

• Use to specify the time in tenths of a second in which the host must respond to a group membership query. The possible period ranges are as follows:
  • IGMPv2: 1–255 tenths of a second
  • IGMPv3: 1–31744 tenths of a second
• IGMPv2 and IGMPv3 include this value in IGMP query messages sent out on the interface.
• You cannot set this value on interfaces running IGMPv1.
• Using a lower value enables members to join and leave groups more quickly.
• Use the IGMP-Max-Resp-Time RADIUS attribute (VSA 26-96) in RADIUS Access-Accept messages as an alternative method of configuring this value. The RADIUS setting takes precedence over a CLI setting.
• Example

  host1:boston(config-if)#ip igmp query-max-response-time 120

• Use the no version to restore the default, 100 tenths of a second (10 seconds).
• See ip igmp query-max-response-time.

ip igmp robustness

• Use to specify the number of times that the router sends each IGMP message from this interface.
• Use a higher value to ensure high reliability from IGMP.
• Specify a number in the range 1–4.
• Example

  host1:boston(config-if)#ip igmp robustness 2

• Use the no version to restore the default, 3.
• See ip igmp robustness.

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