I have attached a network diagram explaining IPTV network , i have below queries to understand & configure IPTV .

  • All ports on edge switches are configured as access ports in VLAN 101.
  • On Core & L-2 switches , configuration is simple (i.e) VLAN , VLAN IP address , Access ports & basic administration configuration.
  • DCM switch is converting analog signal from head end to IP.

Recently added 50 IPTVs as expansion , due to which flickering/latentcy - mainly BW related issue were seen. As a recommendation from vendor , Multicast needs to be enabled.I have tried understanding L-2 Multicast on cisco portal , however unable to understand what needs to configured on Cisco Core & Edge.

  • What can be the recommendation for implementation for IP/layer-2 Multicast?
  • What is IGMP snooping & IGMP querier?
  • What does ip igmp snooping querier & ip igmp snooping command ?

Thanks in advance



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1 Answer 1


When running in multicast mode, you will only need to carry one copy of each channel being watched down to the 2960, rather than one stream per attached TV Set.

Depending on the total number of channels (worst case: every TV attached to the 2960 is watching a different channel/stream) you may still need to distribute TVs across multiple access switches.

It's not clear from your diagram whether VLAN 101 extends up to the Cisco DCM switch or not, but let's assume it does.

You need to designate one of your nodes as an IGMP querier - I would recommend setting this on the VLAN 101 interface of the 4507, as if you expand in future (with more 2960s) it's likely that they'll be attached to this switch.

The IGMP querier listens out for IGMP messages from end devices (such as your TVs) and records which downstream ports are interested in receiving which multicast groups (one per stream/channel).

IGMP-Snooping on the other hand should be enabled in VLAN 101 on each 2960 so that the switch doesn't simply flood all received streams out to all TVs.

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