I recently put an IOS access list on my 2600 router blocking TCP ports 139 and 445, which basically worked as advertised. An unintentional side effect of this access list was to disable incomming ICMP (ping) traffic as well. I have spent some time trying to figure out why this is happening, with almost no success. Would an ICMP permit statement ahead of the tcp deny statements in the ACL resolve this problem? Additionally why would ICMP be using these ports?
