Configure Networking

2023-07-07T10:27:22Z

Nazar-pc: Note that ifupdown-ng is required for new syntax of `/etc/network/interfaces`

This page will assist you in setting up networking on Alpine Linux.
{{Note|You must be logged in as root in order to perform the actions on this page.}}

= Setting System Hostname =
To set the system hostname:
{{Cmd|echo "shortname" > /etc/hostname}}

Then, to activate the change:
{{Cmd|hostname -F /etc/hostname}}

If you're using IPv6, you should also add the following special IPv6 addresses to your <code>/etc/hosts</code> file:
<pre>::1 localhost ipv6-localhost ipv6-loopback
fe00::0 ipv6-localnet
ff00::0 ipv6-mcastprefix
ff02::1 ipv6-allnodes
ff02::2 ipv6-allrouters
ff02::3 ipv6-allhosts</pre>

{{Tip|If you're going to use automatic IP configuration, such as IPv4 DHCP or IPv6 Stateless Autoconfiguration, you can skip ahead to [[#Configuring_DNS|Configuring DNS]]. Otherwise, if you're going to use a static IPv4 or IPv6 address, continue below.}}

For a static IP configuration, it's common to also add the machine's hostname you just set (above) to the <code>/etc/hosts</code> file.

Here's an IPv4 example:
<pre>192.168.1.150 shortname.domain.com</pre>

And here's an IPv6 example:
<pre>2001:470:ffff:ff::2 shortname.domain.com</pre>

= Configuring DNS =
{{Tip|'''For users of IPv4 DHCP:''' Please note that <code>/etc/resolv.conf</code> will be completely overwritten with any nameservers provided by DHCP.
If DHCP does not provide any nameservers, then <code>/etc/resolv.conf</code> will still be overwritten, but will not contain any nameservers!}}

For a static IP address and static nameservers, use one of the following examples.

For IPv4 nameservers, edit your <code>/etc/resolv.conf</code> file to look like this:<br />
The following example uses [http://en.wikipedia.org/wiki/Google_Public_DNS Google's Public DNS servers].
nameserver 8.8.8.8
nameserver 8.8.4.4

For IPv6 nameservers, edit your <code>/etc/resolv.conf</code> file to look like this:<br />
The following example uses [http://www.he.net/ Hurricane Electric's] public DNS server.
nameserver 2001:470:20::2
You can also use Hurricane Electric's public IPv4 DNS server:
nameserver 74.82.42.42

{{Tip|If you decide to use Hurricane Electric's nameserver, be aware that it is 'Google-whitelisted'. What does this mean? It allows you access to many of Google's services via IPv6. (Just don't add other, non-whitelisted, nameservers to <code>/etc/resolv.conf</code> — ironically, such as Google's Public DNS Servers.) Read [http://www.google.com/intl/en/ipv6/ here] for more information.}}

= Enabling IPv6 (Optional) =

If you use IPv6, do the following to enable IPv6 now and at each boot:
{{Cmd|modprobe ipv6
echo "ipv6" >> /etc/modules}}

= Interface Configuration =

== Loopback Configuration (Required) ==
{{Note|The loopback configuration must appear first in <code>/etc/network/interfaces</code> to prevent networking issues.}}
To configure loopback, add the following to a new file <code>/etc/network/interfaces</code>:
<pre>auto lo
iface lo inet loopback</pre>

The above works to set up the IPv4 loopback address (127.0.0.1), and the IPv6 loopback address (<code>::1</code>) — if you enabled IPv6.

== Wireless Configuration ==

See [[Connecting to a wireless access point]].

== Ethernet Configuration ==
For the following Ethernet configuration examples, we will assume that you are using Ethernet device <code>eth0</code>.

=== Initial Configuration ===
Add the following to the file <code>/etc/network/interfaces</code>, above any IP configuration for <code>eth0</code>:
<pre>auto eth0</pre>

=== IPv4 DHCP Configuration ===
Add the following to the file <code>/etc/network/interfaces</code>, below the <code>auto eth0</code> definition:
<pre>iface eth0 inet dhcp</pre>
By default, the busybox DHCP client (udhcpc) requests a static set of options from the DHCP server. If you need to extend this set, you can do so by setting some additional command line options for the DHCP client, via the <code>udhcpc_opts</code> in your interface configuration. The following example requests
<code>domain-search</code> option:
<pre>iface eth0 inet dhcp
udhcpc_opts -O search</pre>
For a complete list of command line options for udhcpc, see [https://busybox.net/downloads/BusyBox.html#udhcpc this document].

=== IPv4 Static Address Configuration ===
Add the following to the file <code>/etc/network/interfaces</code>, below the <code>auto eth0</code> definition:

<pre>iface eth0 inet static
address 192.168.1.150
netmask 255.255.255.0
gateway 192.168.1.1</pre>

Since Alpine 3.13 (and only if you have <code>ifupdown-ng</code> installed) must be:

<pre>iface eth0 inet static
address 192.168.1.150/24
gateway 192.168.1.1</pre>

==== Additional IP addresses ====

<pre>iface eth0 inet static
address 192.168.1.150
netmask 255.255.255.0

iface eth0 inet static
address 192.168.1.151/24
</pre>

Since Alpine 3.13 (and only if you have <code>ifupdown-ng</code> installed) must be:

<pre>iface eth0 inet static
address 192.168.1.150/24
gateway 192.168.1.1

iface eth0 inet static
address 192.168.1.151/24
</pre>

=== IPv6 DHCP Configuration ===
Alpine's use of ifupdown-ng supports three DHCP clients: udhcpc, dhclient, and dhcpcd. Of these, only dhcpcd can interact with both DHCP and DHCPv6 from the same process, which ifupdown-ng requires. Thus the IPv4 DHCP configuration given above will also result in the use of DHCPv6, but only if you install the dhcpcd package. (The ifupdown-ng scripts prioritize dhclient over udhcpc, and they prioritize dhcpcd over dhclient; see <code>/usr/libexec/ifupdown-ng/dhcp</code>.)

=== IPv6 Stateless Autoconfiguration ===
Add the following to the file <code>/etc/network/interfaces</code>, below the <code>auto eth0</code> definition:
<pre>iface eth0 inet6 auto</pre>

=== IPv6 Static Address Configuration ===
Add the following to the file <code>/etc/network/interfaces</code>, below the <code>auto eth0</code> definition:

<pre>iface eth0 inet6 static
address 2001:470:ffff:ff::2
netmask 64
gateway 2001:470:ffff:ff::1
pre-up echo 0 > /proc/sys/net/ipv6/conf/eth0/accept_ra</pre>

Since Alpine Linux 3.13 (and only if you have <code>ifupdown-ng</code> installed) must be as:

<pre>iface eth0 inet6 static
address 2001:470:ffff:ff::2/64
gateway 2001:470:ffff:ff::1
pre-up echo 0 > /proc/sys/net/ipv6/conf/eth0/accept_ra</pre>

== Example: Dual-Stack Configuration ==

This example shows a dual-stack configuration.

<pre>auto lo
iface lo inet loopback

auto eth0

iface eth0 inet static
address 192.168.1.150
netmask 255.255.255.0
gateway 192.168.1.1

iface eth0 inet6 static
address 2001:470:ffff:ff::2
netmask 64
gateway 2001:470:ffff:ff::1
pre-up echo 0 > /proc/sys/net/ipv6/conf/eth0/accept_ra</pre>

Take care since Alpine 3.13 (and only if you have <code>ifupdown-ng</code> installed) must be as:

<pre>auto lo
iface lo inet loopback

auto eth0

iface eth0 inet static
address 192.168.1.150/24
gateway 192.168.1.1

iface eth0 inet6 static
address 2001:470:ffff:ff::2/64
gateway 2001:470:ffff:ff::1
pre-up echo 0 > /proc/sys/net/ipv6/conf/eth0/accept_ra</pre>

= Firewalling with iptables and ip6tables =

See also: [[Alpine Wall]] - [[How-To Alpine Wall]] - [[Alpine Wall User's Guide]]

== Install iptables/ip6tables ==
* To install iptables:
: {{Cmd|apk add iptables}}

* To install ip6tables:
: {{Cmd|apk add ip6tables}}

* To install the man pages for iptables and ip6tables:
: {{Cmd|apk add iptables-doc}}

== Configure iptables/ip6tables ==

== Save Firewall Rules ==

=== For iptables ===
# Set iptables to start on reboot
#* {{ Cmd| rc-update add iptables }}
# Write the firewall rules to disk
#* {{ Cmd| /etc/init.d/iptables save}}
# If you use Alpine Local Backup:

## Save the configuration
##* {{ Cmd| lbu ci }}

=== For ip6tables ===
# Set ip6tables to start on reboot
#* {{ Cmd| rc-update add ip6tables }}
# Write the firewall rules to disk
#* {{ Cmd| /etc/init.d/ip6tables save}}
# If you use Alpine Local Backup:

## Save the configuration
##* {{ Cmd| lbu ci }}

= Activating Changes and Testing Connectivity =
Changes made to <code>/etc/network/interfaces</code> can be activated by running:
{{Cmd|/etc/init.d/networking restart}}
If you did not get any errors, you can now test that networking is configured properly by attempting to ping out:
{{Cmd|ping www.google.com}}
<pre>PING www.l.google.com (74.125.47.103) 56(84) bytes of data.
64 bytes from yw-in-f103.1e100.net (74.125.47.103): icmp_seq=1 ttl=48 time=58.5 ms
64 bytes from yw-in-f103.1e100.net (74.125.47.103): icmp_seq=2 ttl=48 time=56.4 ms
64 bytes from yw-in-f103.1e100.net (74.125.47.103): icmp_seq=3 ttl=48 time=57.0 ms
64 bytes from yw-in-f103.1e100.net (74.125.47.103): icmp_seq=4 ttl=48 time=60.2 ms
^C
--- www.l.google.com ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3007ms
rtt min/avg/max/mdev = 56.411/58.069/60.256/1.501 ms</pre>

For an IPv6 traceroute (<code>traceroute6</code>), you will first need to install the <code>iputils</code> package:
{{Cmd|apk add iputils}}

Then run <code>traceroute6</code>:
{{Cmd|traceroute6 ipv6.google.com}}
<pre>traceroute to ipv6.l.google.com (2001:4860:8009::67) from 2001:470:ffff:ff::2, 30 hops max, 16 byte packets
1 2001:470:ffff:ff::1 (2001:470:ffff:ff::1) 3.49 ms 0.62 ms 0.607 ms
2 * * *
3 * * *
4 pr61.iad07.net.google.com (2001:504:0:2:0:1:5169:1) 134.313 ms 95.342 ms 88.425 ms
5 2001:4860::1:0:9ff (2001:4860::1:0:9ff) 100.759 ms 100.537 ms 89.907 ms
6 2001:4860::1:0:5db (2001:4860::1:0:5db) 115.563 ms 102.946 ms 106.191 ms
7 2001:4860::2:0:a7 (2001:4860::2:0:a7) 101.754 ms 100.475 ms 100.512 ms
8 2001:4860:0:1::c3 (2001:4860:0:1::c3) 99.272 ms 111.989 ms 99.835 ms
9 yw-in-x67.1e100.net (2001:4860:8009::67) 101.545 ms 109.675 ms 99.431 ms</pre>

= Additional Utilities =

== iproute2 ==

You may wish to install the 'iproute2' package (note that this will also install iptables if not yet installed)

{{Cmd|apk add iproute2}}

This provides the 'ss' command which is IMHO a 'better' version of netstat.

Show listening tcp ports:
{{Cmd|ss -tl}}

Show listening tcp ports and associated processes:
{{Cmd|ss -ptl}}

Show listening and established tcp connections:
{{Cmd|ss -ta}}

Show socket usage summary:
{{Cmd|ss -s}}

Show more options:
{{Cmd|ss -h}}

== drill ==

You may also wish to install 'drill' (it will also install the 'ldns' package) which is a superior (IMHO) replacement for nslookup and dig etc:

{{Cmd|apk add drill}}

Then use it as you would for dig:

{{Cmd|drill alpinelinux.org @8.8.8.8}}

To perform a reverse lookup (get a name from an IP) use the following syntax:

{{Cmd|drill -x 8.8.8.8 @208.67.222.222}}

= Related articles =

You may also wish to review the following network related articles:

[[Vlan|VLAN setup]]

[[Bonding|Bonding setup]]

[[Bridge|Network bridge setup]]

[[udhcpc|udhcpc configuration]]

[[Category:Networking]]

Alpine Linux - User contributions [en]

Configure Networking