Cisco ASA 5505 - Manual (Page 500)

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Cisco ASA 5500 Series Configuration Guide using the CLI
Chapter 26 Configuring Multicast Routing
Customizing Multicast Routing
Modifying the Query Messages to Multicast Groups
Note The igmp query-timeout and igmp query-interval commands require IGMP Version 2.
The ASA sends query messages to discover which multicast groups have members on the networks
attached to the interfaces. Members respond with IGMP report messages indicating that they want to
receive multicast packets for specific groups. Query messages are addressed to the all-systems multicast
group, which has an address of 224.0.0.1, with a time-to-live value of 1.
These messages are sent periodically to refresh the membership information stored on the ASA. If the
ASA discovers that there are no local members of a multicast group still attached to an interface, it stops
forwarding multicast packet for that group to the attached network, and it sends a prune message back
to the source of the packets.
By default, the PIM designated router on the subnet is responsible for sending the query messages. By
default, they are sent once every 125 seconds.
When changing the query response time, by default, the maximum query response time advertised in
IGMP queries is 10 seconds. If the ASA does not receive a response to a host query within this amount
of time, it deletes the group.
To change the query interval, query response time, and query timeout value, perform the following steps:
Detailed Steps
Command Purpose
igmp limit number
Example:
hostname(config-if)# igmp limit 50
Limits the number of IGMP states on an interface.
Valid values range from 0 to 500, with 500 being the default value. Setting
this value to 0 prevents learned groups from being added, but manually
defined memberships (using the igmp join-group and igmp static-group
commands) are still permitted. The no form of this command restores the
default value.
Command Purpose
Step 1 igmp query-interval seconds
Example:
hostname(config-if)# igmp query-interval
30
Sets the query interval time in seconds.
Valid values range from 0 to 500; 125 is the default value.
If the ASA does not hear a query message on an interface for the
specified timeout value (by default, 255 seconds), then the ASA
becomes the designated router and starts sending the query
messages.