Guide to Unix/Commands/Networking

ifconfig
Configures a network interface.

Links:
 * ifconfig, freebsd.org
 * ifconfig, manpages.ubuntu.com

ifdown
Brings a network interface down. See also.

Links:
 * iup, ss64.com

ifup
Brings a network interface up. See also.

Links:
 * iup, ss64.com

ping
Sends ICMP packets to network hosts, mostly to see whether they are up.

Examples:
 * ping www.wikibooks.org

Links:
 * ping, freebsd.org
 * 6 ping: Packets to network hosts in GNU Inetutils manual, gnu.org
 * ping (networking utility)