---
tags: [networks, internet, Debian, linux, Ethernet]
---

## Ethernet

First identify the name of your Ethernet interface with
[`ip addr show`](./View_IP_addresses.md). Example output:

```
 enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 40:b0:34:37:40:40 brd ff:ff:ff:ff:ff:ff
    inet 192.168.178.53/24 brd 192.168.178.255 scope global enp1s0
```

That last line is configured via `/etc/network/interfaces`. If you have not set
this up, the top line will say `DOWN` instead of `UP` and you will not have
internet access over Ethernet.

The follwing example of `/etc/network/interfaces` is a common default:

```
auto enp1s0
iface enp1s0 inet static
    address 192.168.178.49
    netmask 255.255.255.0
    gateway 192.168.178.1
    dns-nameservers 8.8.8.8 8.8.4.4
```

Sets the following:

- connect automatically as soon as Ethernet port activated
- use the `enp1s0` interface and insist on static IP from [DHCP](./DHCP.md)
- use the static IP address `192.168.178.49`
- use standard subnet masking
- use Google as the preferred and fallback DNS

Restart networking:

```sh
sudo systemctl restart networking
```

Confirm connection again with `ip addr show` or
`sudo systemctl status networking`.

## Turn the Ethernet interface on/off

```sh
ifup enp1s0
ifdown enp1s0
```

### Use dynamic local IP address

If you don't want to use a static IP, the contents of `/etc/network/interfaces`
is more minimal:

```
auto enp1s0
iface enp1s0 inet dhcp
```

Basically you just let DHCP do the work of negotiating the IP address from the
router.

## Contrast with other Linux operating systems

Arch uses `systemd-resolvd` and NetworkManager. You won't find
`etc/network/interfaces`.

To check network status on Arch use:

```sh
systemctl status NetworkManager
```