M A G N U M 6 K S W I T C H E S , M N S - 6 K U S E R G U I D ESince the query and the join information is exchanged between the neighboring switches, thetopology does not matter. The design issue to consider is the timing difference between atopology recovery and IGMP refresh (recovery). GarrettCom Magnum 6K family of switches,connected in an S-Ring topology recovers very rapidly (sub-second recovery). The IGMP requestsfor updates are sent out every few seconds (depending on the network and the devices on thenetwork). The recovery of the network from a fault situation is much faster than the age out andjoin request from IGMP. Thus when the Magnum 6K switch network self heals, it is possible thatthe video may freeze till the (IGMP) device reissues a join request again.A few additional facts about IGMP L2• GarrettCom Magnum 6K family of switches configured for IGMP-L2 can perform theJoin aggregation required by IGMP• Multicast forwarding is done based on MAC addresses – so datagram to IP addresses224.1.2.3 and 239.129.2.3 can be forwarded on the same port groups. It is not possible todo forwarding based on IP addresses as the Magnum 6K family of switches operate atLayer-2• Magnum 6K family of switches, configured for IGMP L2 are aware of IP address range224.0.0.x as well as MAC address range 01:00:5e:00:00:xx aware as required by RFC 4541• The Magnum 6K family of switches, configured for IGMP L2 support forwarding toports on which multicast routers are attached in addition to the ports where IGMP joinshave been received. Thus IGMP L2 and IGMP L3 networks can co-exist• The Magnum 6K family of switches, configured for IGMP L2 are aware of topologychanges, so new queries can be sent or tables updated to ensure robustnessConfiguring IGMPSyntax igmp – IGMP configuration modeSyntax igmp - enable or disable IGMP on the switchSyntax show igmp – IGMP operation statusSyntax mcast - enable or disable unknown multicast streams. The default is enabledSyntax mode= - set the IGMP mode. Normal is when a L3 device is in the network and isthe IGMP root. The IGMP-L2 is used when there is no L3 device in the networkSyntax group add ip= port= vlan= - add ports to aspecific IGMP broadcast221
