We have a number of our Restaurants using the RVS4000. We recently scanned the restaurants to become PCI compliant and the ones using the RVS4000 routers failed due to the possibility of UDP packets being injected on port 53 despite the presence of a firewall.
I tried to configure the Firewall to block port 53, but a new scan revealed the same problem.
I called Cisco and they advised me to upgrade the firmware but they could not tell me if this actually solved the problem. I would rather not do this unless it is absolutely necessary.