We have a cisco 3845 Router. We have 2 proxies running and both are given a one to one nat on the router. Last week an IP NAT rule of the first proxy has disappeared from the running config, but still listed in the startup. We have restarted and the issue is fixed for 4 days. After that the IP nat rule of the second proxy has been disappeared all of a sudden from Running. Instead of restarting we have manually entered the rule and it worked for half an hour. Again disappeared. Restarted. We have assigned another public ip for the second proxy and it worked for 3-4 days. After that again disappeared. Kindly advice what could be the issue.