IP and Routing: The ip Command

The ip command is the modern replacement for ifconfig, route, and several other older tools. It’s been the standard on Linux for over a decade. If you still use ifconfig, learn ip — it’s faster, more capable, and what every modern doc references.

Show all interfaces and addresses

ip a                # show all addresses (most common)
ip addr             # same thing, longer form
ip -br a            # brief table view
ip -c a             # colored output
ip -4 a             # only IPv4
ip -6 a             # only IPv6

Output gives you each interface with its IP, MAC, MTU, and state.

Show just one interface

ip a show eth0
ip a show wlan0

Bring an interface up or down

sudo ip link set eth0 up
sudo ip link set eth0 down

ip link             # show all links (interfaces) and their states
ip -br link         # brief view

Add or remove an IP address

# Add an IP (temporary — gone on reboot)
sudo ip addr add 192.168.1.50/24 dev eth0

# Remove
sudo ip addr del 192.168.1.50/24 dev eth0

Permanent changes belong in your distro’s network config (Netplan on Ubuntu, NetworkManager / nmcli on Fedora, /etc/network/interfaces on plain Debian).

Show routing table

ip route            # show routes (most common)
ip r                # short form
ip -4 r             # IPv4 routes
ip route get 8.8.8.8    # how would I reach this IP?

Sample output:

default via 192.168.1.1 dev wlan0
192.168.1.0/24 dev wlan0 proto kernel scope link src 192.168.1.42

The first line is the default route — anything not matching another route goes here.

Add or change a route

# Add a static route to 10.0.0.0/8 via gateway
sudo ip route add 10.0.0.0/8 via 192.168.1.254

# Change the default gateway
sudo ip route del default
sudo ip route add default via 192.168.1.1

# Remove a route
sudo ip route del 10.0.0.0/8

ARP table (who has which IP)

ip neigh            # show ARP table
ip n                # short
arp -a              # legacy command, still works

Bridges, VLANs, namespaces (advanced)

ip link add br0 type bridge        # create a bridge interface
ip link add link eth0 name eth0.10 type vlan id 10   # VLAN 10 on eth0
ip netns add mynamespace            # network namespace

NetworkManager command-line: nmcli

If your system uses NetworkManager (most desktops, Fedora, Ubuntu Desktop), nmcli is the way to make persistent changes:

nmcli device                       # list devices and state
nmcli connection show              # configured connections
nmcli connection up "MyWiFi"
nmcli device wifi list              # scan
nmcli device wifi connect "SSID" password "yourpass"

Useful one-liners

# Get YOUR machine's primary IP
ip route get 1.1.1.1 | awk 'NR==1 {print $7}'

# Find your default gateway
ip route | awk '/default/ {print $3}'

# Find your active interface name
ip route | awk '/default/ {print $5}'

# Get external (public) IP
curl -s ifconfig.me

Common mistakes

• Editing IP with ip addr add and expecting it to survive reboot — it doesn’t. Use your distro’s permanent config.
• Using ifconfig on a server where it’s no longer installed — switch to ip a.
• Confusing ip a (addresses) with ip link (interfaces) — they show overlapping but different info.

What to learn next

Once you can read IPs, the next concern is sockets and ports — what’s listening, what’s connected. The ss command handles that.