Controlling Access To Multicast Groups; Limiting The Number Of Igmp States On An Interface; Modifying The Query Interval And Query Timeout - Cisco 7604 Configuration Manual

Configuring IGMP Features

Controlling Access to Multicast Groups

To control the multicast groups that hosts on the FWSM interface can join, perform the following steps:
Create an access list for the multicast traffic. You can create more than one entry for a single access list.
Step 1
You can use extended or standard access lists.
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Apply the access list to an interface by entering the following command:
Step 2
hostname(config-if)# igmp access-group acl
The acl argument is the name of a standard or extended IP access list.

Limiting the Number of IGMP States on an Interface

You can limit the number of IGMP states resulting from IGMP membership reports on a per-interface
basis. Membership reports exceeding the configured limits are not entered in the IGMP cache and traffic
for the excess membership reports is not forwarded.
To limit the number of IGMP states on an interface, enter the following command:
hostname(config-if)# igmp limit number
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.

Modifying the Query Interval and Query Timeout

The FWSM 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 FWSM. If the
FWSM 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. To change this interval, enter the following command:
Catalyst 6500 Series Switch and Cisco 7600 Series Router Firewall Services Module Configuration Guide using ASDM
9-4
To create a standard access list, enter the following command:
hostname(config)# access-list name standard [permit | deny] ip_addr mask
The ip_addr argument is the IP address of the multicast group being permitted or denied.
To create an extended access list, enter the following command:
hostname(config)# access-list name extended [permit | deny] protocol src_ip_addr
src_mask dst_ip_addr dst_mask
The dst_ip_addr argument is the IP address of the multicast group being permitted or denied.
Chapter 9 Configuring Multicast Routing
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