Multicast operates in three vlan checking modes.
Mode 1 - Do no vlan checking. The sender and
receivers do not have to be on the same vlan.
Multicast connections in this mode disregard
whether or not the sender or receiver is in a
secure or open vlan.
Mode 2 - Do some vlan checking. This mode allows
connections to be established between any
sender/receivers on any vlan except for groups
using the 224.0.0.x range of ip multicast
addresses. These addresses are used for the
most part by routers which should only be
communicating to each other when they are
in the same vlan. Mode 2 restricts routers
to have the same port based vlan membership.
Mode 3 - Check all. The sender and receivers have
to be members of the same port based vlan.
This setting takes effect immediately. No existing
connections will be torn down.