Reference Guide

Multicast Features | 627
In Figure 33-2, 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.
Dell Networking OS Behavior: Do not enter the command ip igmp access-group before creating the access-list. If
you do, upon entering your first deny rule, Dell Networking OS clears 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 command ip igmp access-group before creating the access-list, prevent Dell Networking OS from
clearing the routing table by entering a permit any rule with high sequence number before you enter any other
rules.