Internet Group Management Protocol (IGMP)

IP networks use IGMP and PIM (Protocol Independent Multicast) to manage multicast traffic across Layer 3 boundaries. When IGMP is enabled on your network, routers and other network devices use it to determine the hosts in the domain that are interested in receiving multicast traffic.

The Vocera server assigns a multicast address to each broadcast session. The device registers to receive the stream and joins the group by sending an IGMP report to the upstream router. The router then adds that group to the list of multicast groups that should be forwarded onto the local subnet. IGMP allows the device to inform the router that it is interested in receiving a particular multicast stream. When a host no longer wants to receive multicast traffic, it sends the router an IGMP Leave message.

If IGMP is enabled on your network and you want to broadcast across subnets, you must also set the B3.BroadcastUsesIGMP True on the badge. Enabling this property allows a badge to register its membership in the appropriate multicast group to receive multicast traffic from other badges, also from another subnet. Vocera broadcast is implemented as IP Multicast. If broadcast commands must cross a subnet, IGMP must be supported in the switch, IP multicast routing on your router and PIM (Protocol Independent Multicast) on your VLANs.

When the badge property V5.ForceIGMPVersion is set, and if Vocera Smartbadge is configured to use IGMPv3, but your network only supports IGMPv2, the Smartbadge negotiates down to IGMPv2 and uses that with the network.

For more information, refer to Vocera Badge Configuration Guide.