Ever wonder why repetitive pings fail after a little while in OS X (e.g. those sent via the -f flag)? By default, OS X has an ICMP rate limit of 250 set. You can increase this or disable, using sysctl. To disable, set the value of net.inet.icmp.icmplim sudo sysctl -w net.inet.icmp.icmplim=0 Happy icmp flooding!