Disable Ping Request (ICMP Echo) in Linux Kernel

Prerequisite

Install the kernel documentation package, if you have not.

$ yum install kernel-doc -y

The package contains several documentation and you can list them all with 'rpm -ql kernel-doc'.

Test Before

$ ping 192.168.122.10
PING 192.168.122.10 (192.168.122.10) 56(84) bytes of data.
64 bytes from 192.168.122.10: icmp_seq=1 ttl=64 time=0.171 ms

Ok. The machine is responding to ping.

Set Kernel Parameter to Ignore Ping (ICMP echo) Request

Now use kernel configuration tool, sysctl, to first list all parameter that contain ICMP.

$ sysctl -a | grep icmp
net.netfilter.nf_conntrack_icmpv6_timeout = 30
net.netfilter.nf_conntrack_icmp_timeout = 30
net.ipv4.icmp_echo_ignore_all = 0
net.ipv4.icmp_echo_ignore_broadcasts = 1
net.ipv4.icmp_ignore_bogus_error_responses = 1
net.ipv4.icmp_errors_use_inbound_ifaddr = 0
net.ipv4.icmp_ratelimit = 1000
net.ipv4.icmp_ratemask = 6168
net.ipv6.icmp.ratelimit = 1000

To find out what each parameter do read the kernel network ip sysctl documentation.

$ grep -A5 icmp /usr/share/doc/kernel-doc-*/Documentation/networking/ip-sysctl.txt 
icmp_echo_ignore_all - BOOLEAN
 If set non-zero, then the kernel will ignore all ICMP ECHO
 requests sent to it.
 Default: 0
...

And to set kernel parameter.

$ sysctl -w net.ipv4.icmp_echo_ignore_all=1

Now test again to ping server and you should not get any respond.

To make the changes permanent.

$ echo "net.ipv4.icmp_echo_ignore_all = 1" >> /etc/sysctl.conf