Dell Force10 E1200i FTOS Version 8.4.1.5 Configuration Guide for ExaScale - Page 596

www.dell.com | support.dell.com In Figure 30-4, the host on Port 1 sends an exclude-that is, exclude nothing-report to join group G and receive traffic from all transmitting sources for the group. FTOS creates a (*,G) entry and lists Port 1 in the outgoing interface list. The host on Port 3 sends an include report to join the same group G, but receive traffic from only source S. FTOS creates a (S,G) entry and could list Port 3 as the outgoing interface. However, inbound traffic matches against the most specific entry, in this case, traffic from source S for group G matches the (S,G) entry. So, this traffic is forwarded out of only Port 3, which means that Port 1, which requested traffic from all sources, would be denied (S,G) traffic. To reconcile this behavior, FTOS adds (*,G) ports to (S, G) entries. These inherited ports are marked with an asterisk to differentiate them from ports that have been snooped. In Figure 30-4, the (S,G) entry inherits Port 1 from the (*,G) entry. Now, (S,G) traffic is forwarded out Ports 1 and 3, so that Port 1 receives traffic from all sources, as requested. Note: IGMPv3 does not inherit ports like MLDv2. Instead, when a VLAN has hosts that want to include and exclude the same source, S, the group defaults to exclude mode. That is, no (S,G) entry installed, and the excluding host receives all traffic. Notice, that in Figure 30-4, the MLD snooping table has an (S,G) entry, while the IGMP snooping does not. 596 | Multicast Listener Discovery