If the entity is performing IGMP proxy, set this field to 'true' to indicate that this is an upstream interface. An interface is an upstream interface if the route towards the root of the IGMP proxy tree goes out of the interface. An IGMP proxy device must not run the router portion of IGMP on an upstream interface. Hence this entity does not run IGMP on an upstream interface, and does not return information about the remote Querier in the objects in the MIB row for an upstream interface. An IGMP proxy device must have an upstream interface. To provide resilience to upstream interface failure, the device might have more than one upstream interface. If so, the device proxies group membership state onto one of the upstream interfaces; the others are standby upstream interfaces, ready to be used if the current upstream interface fails. The upstream interface to use is chosen by the MRPM entity that this entity is joined to. If the value of this object changes while this interface is active, this entity will deactivate the interface, then reactivate it using the new value. The change of value might cause a change to the upstream interface chosen by the MRPM entity, so there might be a temporary data outage while the new data path is set up across the network. If the entity is not performing IGMP proxy, this field has no effect.