An IP router capable of isochronous switching of a packetized media stream. According to an example, the IP router parses the RTP header within an incoming IP datagram to extract the RTP time stamp, which provides a time value for a unique IP Flow. By inspecting the header, the IP router can switch the flow at the point in time that the RTP time stamp value changes, or matches a target value. In one aspect, the IP router looks for the change in the RTP time stamp value and performs the switch based on the detected change. In another aspect, the IP router performs the switch at a specified time stamp value that can be unique to a group of signals or based on a common “sync” value published to all the ports of the IP router.