ip Command on ChromeOS Linux Environment

The ip command is a modern and robust utility for network configuration and management, replacing legacy tools like ifconfig. It provides extensive functionality for configuring and monitoring network interfaces, routing tables, and more. On ChromeOS Linux (Crostini), the ip command is an essential tool for handling networking tasks.

Syntax

The basic syntax of the ip command is:

ip [options] object [command]

Key Components:

object: Specifies the network object to interact with (e.g., link, addr, route).
command: Defines the action to perform on the object (e.g., add, show, del).
options: Modify the behavior or output of the command.

Examples of Usage

Display All Network Interfaces

To list all network interfaces and their details:

ip addr show

Example Output:

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default
    inet 127.0.0.1/8 scope host lo
    inet6 ::1/128 scope host
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default
    inet 192.168.1.100/24 brd 192.168.1.255 scope global eth0
    inet6 fe80::1e6f:65ff:fe7a:1c21/64 scope link

Enable a Network Interface

To bring a network interface up:

sudo ip link set eth0 up

Disable a Network Interface

To bring a network interface down:

sudo ip link set eth0 down

Assign an IP Address to an Interface

To assign a specific IP address to a network interface:

sudo ip addr add 192.168.1.150/24 dev eth0

Remove an IP Address from an Interface

To remove a specific IP address:

sudo ip addr del 192.168.1.150/24 dev eth0

View Routing Table

To display the current routing table:

ip route show

Add a Default Gateway

To add a default gateway:

sudo ip route add default via 192.168.1.1

Delete a Route

To remove a specific route:

sudo ip route del 192.168.1.0/24 dev eth0

Objects and Their Commands

`link`

Manages network interfaces.

Show all links:
```
ip link show
```
Change MTU:
```
sudo ip link set eth0 mtu 1400
```

`addr`

Manages IP addresses.

Add or remove an address:

sudo ip addr add 192.168.1.150/24 dev eth0
sudo ip addr del 192.168.1.150/24 dev eth0

`route`

Manages routing tables.

Add a route:

sudo ip route add 192.168.2.0/24 via 192.168.1.1 dev eth0

Show routes:
```
ip route show
```

`neigh`

Manages ARP (Address Resolution Protocol) entries.

Show ARP table:
```
ip neigh show
```

Add an entry:

sudo ip neigh add 192.168.1.10 lladdr 00:1a:2b:3c:4d:5e dev eth0

Troubleshooting

Interface Not Found

If a specified interface is not recognized, list all available interfaces:

ip link show

Permission Denied

Some commands require administrative privileges. Use sudo when necessary:

sudo ip addr add 192.168.1.150/24 dev eth0

Persisting Changes

Changes made with ip are temporary and reset after a reboot. Use network configuration files or scripts for permanent changes.

Best Practices

Use Descriptive Commands: The ip command’s structure ensures clarity. Combine options and objects for precise operations.
Test Before Automating: Always test commands interactively before adding them to scripts.
Document Changes: Keep track of network changes for easier debugging and management.

The ip command is a versatile and modern tool for network configuration and management. By mastering its options and objects, ChromeOS users can efficiently handle networking tasks, ensuring robust and flexible connectivity.