A method of debugging an active unit in a computer system having an active unit for routing computer connections and a standby unit configured to route computer connections in the event the active unit fails. The method comprises the standby unit receiving synchronization data from the active unit in the form of update messages; storing the received synchronization data in local storage; receiving a request for data to be used to perform debugging on the active unit; searching local storage for the requested data; if the requested data is found on the local storage then returning that data to the source of the request; if the requested data is not found on the local storage then requesting the requested data from the active unit, receiving the requested data from the active unit, and returning the received requested data to the source of the request.