Sometimes you may want to disable ping response for many reasons, may be for a security reason… This article explains how do I disable the ping response on Linux ?

Disable ping response Temporarily

To disable the PING response, login as root and type the following command

# echo 1 >/proc/sys/net/ipv4/icmp_echo_ignore_all

To reenable the PING response do this:

# echo 0 >/proc/sys/net/ipv4/icmp_echo_ignore_all

Disable ping response Permanently

Edit the /etc/sysctl.conf file and add the following line

net.ipv4.conf.icmp_echo_ignore_all = 1

Execute sysctl -p to enforce this setting immediately

# sysctl -p

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By default, Linux distribution such as Redhat, CentOS, and Fedora will have IP Forwarding disabled. The need to forward IP packets from one source to another using linux as the default gateway or linux router, IP forwarding should be enabled from this considerations. There are several techniques to enable IP Forwarding.

Check IP Forwarding status

Type the following command

[root@lifelinux ~]# sysctl -l | grep ip_forward

Sample outputs

net.ipv4.ip_forward = 0

or checking out the value in the /proc system

[root@lifelinux ~]# cat /proc/sys/net/ipv4/ip_forward
0

If IP forwarding is disabled, a value of 0 would be displayed and if IP forwarding was recently enabled, linux should be displaying a numerical value of 1.

Enable IP Forwarding temporarily

Login as root and type the following command

[root@lifelinux ~]# echo 1 > /proc/sys/net/ipv4/ip_forward

The setting is changed instantly but this setting will be erased after the reboot.

Enable IP Forwarding permanently

Type the following command

[root@lifelinux ~]# vi /etc/sysctl.conf

Add the following line

net.ipv4.ip_forward = 1

To enable the changes made in sysctl.conf you will need to run the command

[root@lifelinux ~]# sysctl -p

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Many malicious attacks begin with a ping scan. Disabling ICMP echo requests prevents your system’s discovery with a ping.

Disable ICMP echo responses temporarily

You can temporarily disable the ICMP using the following method but this setting will be erased after the reboot.

root@lifelinux:~# echo 1 >  /proc/sys/net/ipv4/icmp_echo_ignore_all

Also, to enable the ICMP echo responses back, type the following command:

root@lifelinux:~# echo 0 >  /proc/sys/net/ipv4/icmp_echo_ignore_all

Disable ICMP echo responses permanently

You can permanently disable the ICMP echo reponses using the following method:
Edit the sysctl.conf file:

root@lifelinux:~# vi /etc/sysctl.conf

And add the following line:

net.ipv4.icmp_echo_ignore_all = 1

After that, execute sysctl -p to enforce this setting immediately:

root@lifelinux:~# sysctl -p

The above command loads the sysctl settings from the sysctl.conf.

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