First, an IGMP querier must exist on the network. The NV-EC1701
supports multicasting, however it also deliberately blocks unknown traffic and allows only those multicast communications listed on a report provided by the querier. To prevent traffic congestion, we do not want all multicast streams on a LAN delivered to all destinations. We want them delivered only to destinations that request the stream. The NV-EC1701
does so by using IGMP snooping and/or multicast broadcasts to determine when to pass a particular multicast stream. Typically, the camera generates more than one stream. Multicast streams are usually used for high-bandwidth communication to the VMS for recording. Unicast streams at slower data rates are usually used for live browser-based monitoring. The software driver in the VMS system generates a broadcast request destined for the camera. Routers and the NV-EC1701
deliver the requests to the camera. But they also learn (and add to their aging tables) the fact that the VMS system is a valid multicast destination. Multicast packets from the camera are then routed to the VMS destination. A simple browser that does not make this request will not see any multicast streams. The same browser will successfully see a unicast stream. NVT Phybridge does have the capability to route all multicast traffic everywhere. This would require custom configuration at the factory, and is not recommended.