A computer-implemented method for highly-scalable, in-network multicasting of load statistics data, the method comprising: receiving, at a hypervisor from an underlay controller, a match-and-action table that is indexed using one or more multicast 'MC' group identifiers and includes one or more special MC headers; detecting, by the hypervisor, a packet carrying statistics data; determining, by the hypervisor, whether the packet includes an MC group identifier, wherein the MC group identifier identifies an MC group that includes one or more recipients of the statistics data; in response to determining that the packet includes the MC group identifier: retrieving, by the hypervisor using the MC group identifier, a special MC header, of the one or more special MC headers, from the match-and-action table; generating, by the hypervisor, an encapsulated packet by encapsulating the packet with the special MC header; and providing, by the hypervisor, the encapsulated packet to an interface controller for transmitting the encapsulated packet to one or more physical switches; detecting, by a physical switch of the one or more physical switches, the encapsulated packet that includes the special MC header; and determining, by the physical switch, that the special MC header includes an identifier of the physical switch, and, in response, using a bitmap associated in the special MC header with the identifier of the physical switch to determine whether or not to replicate the encapsulated packet on each output port of the physical switch. receiving, at a hypervisor from an underlay controller, a match-and-action table that is indexed using one or more multicast 'MC' group identifiers and includes one or more special MC headers; detecting, by the hypervisor, a packet carrying statistics data; determining, by the hypervisor, whether the packet includes an MC group identifier, wherein the MC group identifier identifies an MC group that includes one or more recipients of the statistics data; in response to determining that the packet includes the MC group identifier: retrieving, by the hypervisor using the MC group identifier, a special MC header, of the one or more special MC headers, from the match-and-action table; generating, by the hypervisor, an encapsulated packet by encapsulating the packet with the special MC header; and providing, by the hypervisor, the encapsulated packet to an interface controller for transmitting the encapsulated packet to one or more physical switches; retrieving, by the hypervisor using the MC group identifier, a special MC header, of the one or more special MC headers, from the match-and-action table; generating, by the hypervisor, an encapsulated packet by encapsulating the packet with the special MC header; and providing, by the hypervisor, the encapsulated packet to an interface controller for transmitting the encapsulated packet to one or more physical switches; detecting, by a physical switch of the one or more physical switches, the encapsulated packet that includes the special MC header; and determining, by the physical switch, that the special MC header includes an identifier of the physical switch, and, in response, using a bitmap associated in the special MC header with the identifier of the physical switch to determine whether or not to replicate the encapsulated packet on each output port of the physical switch.