An apparatus and method for traversing a network address translation/firewall device to maintain a registration between first and second devices separated by the firewall device are provided. In one example, the method includes intercepting a registration message from the first device to the second device. A determination is made based on a first timeout period defined by the second device as to whether it is time to renew the first device's registration. If it is time to renew the first device's registration, the registration message is forwarded to the second device. A response message that includes the first timeout period is intercepted, and the first timeout period is replaced with a second timeout period based on a binding lifetime of the firewall device before forwarding the response message to the first device.