A Linux server is only useful if it can talk on the network, so Linux+ expects you to view and change addresses, routes, hostnames and name resolution with the tools found on current distributions. The key idea is that some commands change the running state only, while others write persistent configuration. Mixing them up is the most common cause of a server that works until its next reboot. The ip command from the iproute2 package replaced older tools such as ifconfig, route and arp. ip addr show (or ip a) lists interfaces and addresses, ip link set eth0 up enables an interface, ip addr add 192.168.10.5/24 dev eth0 adds an address, ip route show displays the routing table, ip route add default via 192.168.10.1 sets a default gateway, and ip neigh shows the ARP (Address Resolution Protocol) neighbor cache. Changes made with ip take effect immediately but are lost at reboot. ss -tulpn complements it by listing listening sockets.
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