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MAGNUM 6K SWITCHES, MNS-6K USER GUIDE
Since the query and the join information is exchanged between the neighboring switches, the
topology does not matter. The design issue to consider is the timing difference between a
topology 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 requests
for updates are sent out every few seconds (depending on the network and the devices on the
network). The recovery of the network from a fault situation is much faster than the age out and
join request from IGMP. Thus when the Magnum 6K switch network self heals, it is possible that
the 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 the
Join aggregation required by IGMP
• Multicast forwarding is done based on MAC addresses – so datagram to IP addresses
224.1.2.3 and 239.129.2.3 can be forwarded on the same port groups. It is not possible to
do forwarding based on IP addresses as the Magnum 6K family of switches operate at
Layer-2
• Magnum 6K family of switches, configured for IGMP L2 are aware of IP address range
224.0.0.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 to
ports on which multicast routers are attached in addition to the ports where IGMP joins
have 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 topology
changes, so new queries can be sent or tables updated to ensure robustness
Configuring IGMP
Syntax igmp – IGMP configuration mode
Syntax igmp <enable| disable> - enable or disable IGMP on the switch
Syntax show igmp – IGMP operation status
Syntax mcast <enable | disable> - enable or disable unknown multicast streams. The default is enabled
Syntax mode= <normal|l2> - set the IGMP mode. Normal is when a L3 device is in the network and is
the IGMP root. The IGMP-L2 is used when there is no L3 device in the network
Syntax group add ip=<group ip> port=<number|list|range> vlan=<vlanid> - add ports to a
specific IGMP broadcast
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