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IGMP (Internet Group Management Protocol) and MLD (Multicast Listener Discovery) snooping allow the bridge to listen to IGMP/MLD communication and make forwarding decisions for multicast traffic based on the received information. By default, bridges are flooding multicast traffic to all bridge ports just like broadcast traffic, which might not always be the best scenario (e.g. for multicast video traffic). The IGMP/MLD snooping tries to solve the problem by forwarding the multicast traffic only to ports where clients are subscribed to, see an IGMP/MLD network concept below. RouterOS bridge is able to process IGMP v1/v2/v3 and MLD v1/v2 packets.
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Basic IGMP snooping configuration
The first example consists only of a single bridge, a single multicast source device, and a couple of multicast client devices. See an network scheme below.
IGMP snooping configuration with VLANs
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