Transparent network devices intercept messages from non-transparent network devices that establish a connection. Transparent network devices modify these messages to establish an inner connection with each other. The transparent network devices mimic at least some of the outer connection messages to establish their inner connection. The mimicked messages and any optional reset messages are intercepted by the transparent network devices to prevent them from reaching the outer connections. Transparent network devices modify network traffic, using error detection data, fragmentation data, or timestamps, so that inner connection network traffic inadvertently received by outer connection devices is rejected or ignored by the outer connection network devices. Transparent network devices may use different sequence windows for inner and outer connection network traffic. To prevent overlapping sequence windows, transparent network devices monitor the locations of the inner and outer connection sequence windows and may rapidly advance the inner connection sequence window as needed.