TuxTraining

Typically if you’re behind a router this will only affect the internal network unless you have some port forwarding going on, but if you’re not behind another router or firewall this can block the outside world from sending ICMP requests to your machine.

To turn answers to icmp_echos (ping) off, as root type:

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

and to turn it on again type:

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

Note: the iptables frontend “Firestarter” enables you do to this via a gui interface as well.

Networking in general can go so in depth that the mind spins thinking about all there is to know, and there’s plenty of linux tools to deal with the simplest of home networks, to complex networking setups. The Linux+ and LPI certification exams require that you already have a working knowledge of networking principles, but they also expect you have a grasp on some of the basic networking tools in the Linux world. Some we’ll cover today, some of these may or may not be included on a specific exam’s test, but none the less, they will aid you in the Unix world.

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Source

Regular ping command only works with IPv4 address. Use ping6 command to send ICMP ECHO_REQUEST to network hosts from a host or gateway.

Type the command as follows:
$ ping6 localhost
$ ping6 host.domain.com
$ ping6 IPv6-address
$ ping6 2001:db8::1428:57ab

Read ping6 man page for more information:
$ man ping6