# Network Configuration
This article is about network configuration in [[gnu-linux|GNU/Linux]] systems

## ifupdown

### Dynamic configurations
Dynamic configuration with ifupdown (IPv4)
```
# /etc/network/interfaces
iface ens3 inet dhcp
```

Dynamic configuration with ifupdwon (IPv6)
```
iface ens3 inet6 auto
```

### Static configurations
Static configuration with ifupdown (IPv4)

```
# /etc/network/interfaces

iface ens3 inet static
    address 10.0.1.115
    netmask 255.255.0.0
    gateway 10.0.0.1
    dns-nameservers 1.1.1.1 8.8.8.8
    dns-search example.com
```

Static configuration with ifupdown (IPv6)
```
iface ens3 inet6 static
    address 2001:db8:1234::10
    netmask 64
    gateway 2001:db8:1234::1
    dns-nameservers 2606:4700:4700::1111 2001:4860:4860::8888
```

Adding extra routes with ifupdown (`up` and `down` run shell commands)
```
iface ens3 inet static
    address 10.0.1.115
    netmask 255.255.0.0
    up ip route add 192.168.100.0/24 via 10.0.0.2
    down ip route del 192.168.100.0/24 via 10.0.2
```

## systemd-networkd
```
[Match]
Name=ens3

[Network]
Address=10.0.1.115/16
Gateway=10.0.0.1
DNS=1.1.1.1
DNS=8.8.8.8

Address=2001:db8:1234::10/64
Gateway=2001:db8:1234::1
DNS=2606:4700:4700::1111
IPv6AcceptRA=no

[Route]
Destination=192.168.100.0/24
Gateway=10.0.0.2
```

## Mapping

 - `iface ens3 inet dhcp` becomes `DHCP=yes` under `[Network]` section
 - `iface ens3 inet6 auto` becomes `IPv6AcceptRA=yes` under `[Network]` section
 - `dns-nameservers` becomes `DNS=` under `[Network]`
 - `up ip route add` becomes `Destionation=` and `Gateway` under `[Route]` section