ip
NetworkPackage: iproute2
Linux's single networking tool: ip addr for addresses and their prefix, ip link for interfaces and their MTU, ip route for the routing table, ip neigh for link neighbours. ip route get <address> is the one that matters — it makes the kernel print the decision it would take, instead of leaving you to infer it. It replaces ifconfig, route and arp, which net-tools supplied and Ubuntu 24.04 no longer installs.
What its options do in the lessons
From the same glossary the lessons render under their commands, so the two cannot disagree.
ip -br- Brief output: one line per interface, with its state and addresses in columns.
ip -br linkis the quickest way to find out what a machine's cards are actually called. ip -o- One line of output per record: each address fits on a single line instead of a paragraph, which makes it readable and usable by
greporawk.
Lessons that teach it
- What actually crosses the wireHow a network works: packets, addresses and neighbours
- Reading a prefix, bit by bitHow a network works: packets, addresses and neighbours
- Neighbour or not: the test run on every packetHow a network works: packets, addresses and neighbours
- When the addresses ran out: the table that rewrites your packetsHow a network works: packets, addresses and neighbours
- The second address family, already running on your machineHow a network works: packets, addresses and neighbours
- Getting an address when you have none yetPorts, TCP and UDP: how two programs talk
- From a name to a byte: five steps, and what each failure provesPorts, TCP and UDP: how two programs talk
- The fix that lasts until the next rebootConfiguring the network: an address that survives a reboot
- A complete static address, without gateway4Configuring the network: an address that survives a reboot
- A second route, and knowing it is the one usedConfiguring the network: an address that survives a reboot
- The MTU: when to lower it, and why never by guessConfiguring the network: an address that survives a reboot
- A bridge: the switch you already haveConfiguring the network: an address that survives a reboot
- Bonding two cards, without doubling the speedConfiguring the network: an address that survives a reboot
- A VLAN is not a subnetConfiguring the network: an address that survives a reboot
- An address that changes machinesConfiguring the network: an address that survives a reboot
- Addresses, interfaces and routesNetworking: how your server is reached