Dell S4048-ON, Configuration Manual

Page: 353 / 1039

Preventing a Host from Joining a Group
You can prevent a host from joining a particular group by blocking specific IGMP reports. Create an extended access list containing
the permissible source-group pairs.
NOTE: For rules in IGMP access lists, source is the multicast source, not the source of the IGMP packet. For IGMPv2,
use the keyword
any
for source (as shown in the following example) because the IGMPv2 hosts do not know in advance
who the source is for the group in which they are interested.
To apply the access list, use the following command.
• Apply the access list.
INTERFACE mode
ip igmp access-group access-list-name
Dell Networking OS Behavior : Do not enter the
ip igmp access-group
command before creating the access-list. If you do,
after entering your first deny rule, Dell Networking OS clears the multicast routing table and re-learns all groups, even those not
covered by the rules in the access-list, because there is an implicit
deny all rule at the end of all access-lists. Therefore, configuring
an IGMP join request filter in this order might result in data loss. If you must enter the
ip igmp access-group
command before
creating the access-list, prevent Dell Networking OS from clearing the routing table by entering a permit any rule with a high
sequence number before you enter any other rules.
In the following example, virtual local area network (VLAN) 400 is configured with an access list to permit only IGMP reports for
group 239.0.0.1. Though Receiver 2 sends a membership report for groups 239.0.0.1 and 239.0.0.2, a multicast routing table entry is
created only for group 239.0.0.1. VLAN 300 has no access list limiting Receiver 1, so both IGMP reports are accepted, and two
corresponding entries are created in the routing table.
Internet Group Management Protocol (IGMP)
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