The "Block Anonymous Internet Requests" blocks any ICMP (internet control message protocol) traffic to the router on the internet side. ICMP controls many aspects of the IP protocol. Through ICMP routers and computers are able to negotiate the MTU, send updates about redirections, routing issues, and more. ICMP is important for IP to work correctly and properly in the internet.
Most people reduce this option to blocking pings on the internet IP address of the router. Pings is the most prominent ICMP message and thus it is often not differentiated between pings and ICMP. Blocking ICMP is supposed to make "invisible" or "not detected" from the internet because the router does not respond to pings. In reality, ICMP and IP work differently because for a computer to be really invisible the router responsible for the destination IP address would send a "destination not reachable". Not responding instead is a good indication that there is something which is simply not responding.
Therefore, block ICMP in the internet can result in connection instabilities because important control messages for IP are blocked and simply ignored. Thus, there is no real benefit blocking ICMP.
Moreover, don't randomly set or change the MTU. There is a way to determine whether your MTU setting makes a problem. Check
this FAQ article for more details.
Message Edited by gv on 06-07-200706:41 PM
