Dell S4048T, Configuration Manual

Page: 434 / 1277

Preventing a Host from Joining a Group
You can prevent a host from joining a particular group by blocking specific IGMP reports using 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, the 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 the 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
Internet Group Management Protocol (IGMP) 434