Preventing a Host from Joining a GroupYou can prevent a host from joining a particular group by blocking specific IGMP reports using an extended access list containing thepermissible 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 thekeyword any forsource (as shown in the following example) because the IGMPv2 hosts do not know in advance who the sourceis for the group in which they are interested.To apply the access list, use the following command.• Apply the access list.INTERFACE modeip igmp access-group access-list-nameDell Networking OS Behavior: Do not enter the ip igmp access-group command before creating the access-list. If you do, afterentering your first deny rule, the Dell Networking OS clears the multicast routing table and re-learns all groups, even those not covered bythe rules in the access-list, because there is an implicit deny all rule at the end of all access-lists. Therefore, configuring an IGMP joinrequest filter in this order might result in data loss. If you must enter the ip igmp access-group command before creating theaccess-list, prevent the Dell Networking OS from clearing the routing table by entering a permit any rule with a high sequence numberbefore 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 group239.0.0.1. 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 onlyfor group 239.0.0.1. VLAN 300 has no access list limiting Receiver 1, so both IGMP reports are accepted and two corresponding entries arecreated in the routing table.Internet Group Management Protocol (IGMP) 377
