Cheatsheet & Examples: ip

The ip command is a powerful utility in Linux for managing network interfaces, routing, and address assignments. It replaces older tools like ifconfig and route.

Display interface information

Example Usage:
ip a
ip addr show

What it does:
Shows details of all network interfaces, including IP addresses, MAC addresses, and status.

Command-line Arguments Explained:

• a: Shorthand for addr (address information).
• show: Displays the requested information.
• dev: Optional flag to filter by a specific interface (e.g., ip a show dev eth0).

Show routing table

Example Usage:
ip route show
ip r

What it does:
Displays the kernel’s routing table, including default routes, networks, and gateways.

Command-line Arguments Explained:

• route: Subcommand to manage routing information.
• show: Displays the routing table.
• r: Shorthand for route.

Add or remove a route

Example Usage:
ip route add default via 192.168.1.1 dev eth0
ip route del 10.0.0.0/24 via 192.168.1.2

What it does:
Modifies the routing table by adding or deleting a route.

Command-line Arguments Explained:

• add: Adds a new route.
• del: Deletes an existing route.
• default: Specifies the default gateway.
• via: Defines the gateway IP address for the route.
• dev: Specifies the network interface used for the route.
• dst: The destination network or IP address (e.g., 10.0.0.0/24).

Manage ARP table entries

Example Usage:
ip neigh show
ip neigh add 192.168.1.1 lladdr 00:11:22:33:44:55 dev eth0

What it does:
Displays or adds entries to the ARP (Address Resolution Protocol) table, which maps IP addresses to MAC addresses.

Command-line Arguments Explained:

• neigh: Subcommand for ARP table management.
• show: Displays the current ARP entries.
• add: Adds a new ARP entry.
• lladdr: The MAC address to associate with the IP.
• dev: The interface where the ARP entry is applied.

Bring a network interface up or down

Example Usage:
ip link set eth0 up
ip link set eth0 down

What it does:
Enables or disables a specific network interface (e.g., eth0).

Command-line Arguments Explained:

• link: Subcommand to manage network interfaces.
• set: Modifies the interface’s properties.
• up: Enables the interface.
• down: Disables the interface.
• eth0: The name of the network interface.

Add an IP address to an interface

Example Usage:
ip addr add 192.168.1.100/24 dev eth0

What it does:
Assigns a new IP address to a specified network interface.

Command-line Arguments Explained:

• addr: Subcommand for address management.
• add: Adds a new IP address.
• 192.168.1.100/24: The IP address and subnet mask.
• dev: Specifies the network interface (e.g., eth0).

List all network devices

Example Usage:
ip link show
ip l

What it does:
Displays all network interfaces and their statuses (up/down, MAC address, etc.).

Command-line Arguments Explained:

• link: Subcommand for interface-level operations.
• show: Displays interface details.
• l: Shorthand for link.

Check interface statistics

Example Usage:
ip -s a
ip -s link show

What it does:
Displays detailed statistics for network interfaces (e.g., packets sent/received).

Command-line Arguments Explained:

• -s: Enables detailed statistics (short for --statistics).
• a: Shorthand for addr (address information).
• link: Subcommand for interface-level operations.
• show: Displays interface details.

Show all IPv4 addresses in brief format

Example Usage:
ip -br a
ip -br addr show

What it does:
Lists IPv4 addresses in a compact, easy-to-read format.

Command-line Arguments Explained:

• -br: Enables brief output mode.
• a: Shorthand for addr.
• show: Displays address information.

Flush routes from the routing table

Example Usage:
ip route flush all
ip route flush cache

What it does:
Clears all routes or the routing cache, forcing the system to relearn routes.

Command-line Arguments Explained:

• flush: Deletes all routes or the routing cache.
• all: Removes all routes.
• cache: Clears the routing cache (not the routing table).