This page covers basic network interfaces, and how to troubleshoot them when they don't work.

ping

You managed to run ping. You have even figured out how to use the -c flag to ping a specific number of times. But if it doesn't work, then what?

Start by checking your networking configuration, which is contained in this file:

/etc/network/interfaces

do it

$ vim /etc/network/interfaces

network device configuration

networking device configurations, if they exist, are located in

/etc/network/interfaces

the file is not required for network hardware to work - it is optional. if nothing is set in the above file, network is probably being managed by network manager. system level daemon that makes things "just work".

desktops/laptops usually want network manager, servers/embedded computers/etc want stuff configured in /etc/network/interfaces

barebones interfaces file:

$ cat /etc/network/interfaces

# The loopback network interface
auto lo
iface lo inet loopback

check for network manager

$ ps ax | grep NetworkManager

option 1: no network manager

kill it! kill it!!!

446 ?        Ssl    0:00 /usr/sbin/NetworkManager --no-daemon

die die die - ok back to what we were doing.

automatic dhcp

if you want to add your ethernet hardware, and let it automatically request and receive an IP address from a DHCP server (this expects/requires the device to be plugged in to something running a DHCP server, like a router)

# The loopback network interface
auto lo
iface lo inet loopback

# Wired connection eth0
auto eth0
iface eth0 inet dhcp

manual static

# The loopback network interface
auto lo
iface lo inet loopback

# Wired connection eth0
auto eth0
iface eth0 inet static
    address 10.10.10.12
    netmask 255.255.248.0
    network 10.10.10.0
    broadcast 10.10.10.255
    gateway 10.10.10.1

the following line changed:

iface eth0 inet static

static, not dhcp

if you declare dhcp, all other configuration details ignored

next declare ip address, 10.10.10.12

declare subnet mask to 255.255.248.0

declare the network we're joining to 10.10.10.0

declare the broadcast ID as 10.10.10.255

decalre the gateway as 10.10.10.1

now restart networking service

$ systemctl restart networking.service

figure out what networking interfaces are available

$ ifconfig 

or 

$ ip addr show

option 2: with network manager

can check if network manager is running:

$ ps aux | grep Network

to configure network manager in a gui-like terminal environment:

$ nmtui

This allows you to connect to a wireless network and enter information into corresponding fields, or to set the details of a static IP address for your network for a particular device. When editing an ethernet connection (like the eth0 device) you will see an IPv4 configuration option. If you pick "Show," you can enter an IP address, a gateway, a DNS server, etc.

Linux/Network Interfaces

From charlesreid1

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