Methods, systems, and computer readable media for supporting a plurality of RTP multiplexing enablement methods in a media gateway are disclosed. According to one aspect, a system includes a media gateway controller configured to receive a signaling message to establish a call from a peer node in a first network, an a media gateway configured to perform a first and second RTP multiplexing enablement process on the media portion of the call, wherein the first RTP multiplexing enablement process includes sending a real-time transport control protocol (RTCP) Application packet to the peer node, refraining from performing RTP multiplexing on packets sent to the peer node until a reply RTCP Application packet is received from the peer node, and receiving RTP multiplexed packets from the peer node, and wherein the second RTP multiplexing enablement process includes obtaining an Internet protocol (IP) realm identifier that identifies the first network, accessing configuration data in the media gateway using the IP realm identifier to determine a predefined multiplexing enablement action for packets destined for the first network, and executing the determined predefined multiplexing enablement action on packets sent to the peer node in the first network.