Block / Deny ICMP Echo (Ping) on Cisco ASA Outside Interface

Most networks that you protect with a Cisco ASA device, will probably want to deny ICMP (maybe not all ICMP types, but a lot of network admins will want to block ICMP Echo, etc.) on the outside interface. This will make the network harder to find through external enumeration, but not impossible.

ASA5505(config)#icmp deny any outside

You will deny ICMP on the outside interface, but if you include ICMP as a protocol in the default global policy map, you can ping from the inside to any host on the outside, and it will be permitted back through the ASA, as it knows about the previous ICMP “connection”.

Mar 15th, 2012 • Posted in 5505, ASA, Best Practices, Security
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