====== IGMP Snooping Groups ======
Apr 2024
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When using IGMP snooping, it can be very useful to see what is happening on the switch. In this example, we can look at a Cisco switch being used in an nCompass Controlled Aquila Live system. It does not matter that we are using nCC, this will look the same on just a Controller based solution also.
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Please bear in mind that this system is 1+1 Encoding Live and 1+1 Multiplexers that are using:
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1. Statistical Multiplexing\\
2. Services Synchronisation\\
3. Dual Output Prevention\\
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This is important to know because we can see the multcasts for each of these processes.
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==== IGMP Snooping Groups ====
Once you have logged in to your switch (in this example I am using a Cisco switch) you can issue this command from the top level (no need to go in to the configuration mode).
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show ip igmp snooping groups
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{{:sh_ip_igmp_snooping_01.png?700|}}
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The VLAN column is which VLAN each of the interfaces is in.
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VLAN 100 - Management (the management interfaces of each server are teamed)
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VLAN 250 - Primary EL output and Mux input
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VLAN 300 - Secondary EL output and Mux input
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VLAN 400 - Mux output VLAN
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We can pick out of the list certain Multicast Groups and their function:
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Vlan Group Type Version Port List
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100 239.211.1.1 igmp v2 Gi0/8, Gi0/13, Gi0/23 - Services Synchronisation (EL)
100 239.211.2.1 igmp v2 Gi0/8, Gi0/13, Gi0/23 - Dual Output Prevention (EL)
100 239.225.0.1 igmp v2 Gi0/15, Gi0/16, Gi0/23 - StatMux Announcer
(EL <-> Mux)
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250 239.1.1.1 igmp v2 Gi0/27, Gi0/28 - Service 01 Multicast (Primary EL)
250 239.1.1.2 igmp v2 Gi0/27, Gi0/28 - Service 02 Multicast (Primary EL)
250 239.1.1.3 igmp v2 Gi0/27, Gi0/28 - Service 03 Multicast (Primary EL)
250 239.1.1.4 igmp v2 Gi0/27, Gi0/28 - Service 04 Multicast (Primary EL)
250 239.225.0.1 igmp v2 Gi0/25, Gi0/26, Gi0/27, Gi0/28 - StatMux Announcer
(EL <-> Mux)
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300 239.2.1.1 igmp v2 Gi0/33, Gi0/34 - Service 01 Multicast (Secondary EL)
300 239.2.1.2 igmp v2 Gi0/33, Gi0/34 - Service 02 Multicast (Secondary EL)
300 239.2.1.3 igmp v2 Gi0/33, Gi0/34 - Service 03 Multicast (Secondary EL)
300 239.2.1.4 igmp v2 Gi0/33, Gi0/34 - Service 04 Multicast (Secondary EL)
300 239.225.0.1 igmp v2 Gi0/31, Gi0/32, Gi0/33, Gi0/34 - StatMux Announcer
(EL <-> Mux)
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400 239.0.0.200 igmp v2 Gi0/37, Gi0/38 - Mux Multicast Output
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