An Ethernet interface module comprises a first full duplex port, a second duplex port, a first path coupling the first duplex port and the second full duplex port, a second path coupling the second full duplex port and the first full duplex port, a first queue disposed in the first path, a second queue disposed in the second path, a third path comprising at least a portion of the first queue coupling the receive and transmit portions of the first port, a fourth path comprising at least a portion of the second queue coupling the receive and transmit portions of the second port, execution apparatus operable responsive to a command to alter the state of said Ethernet interface module, or the contents of said received frame to produce a return frame comprising fields of a received frame that are modified, or both.