How to configure ethernet interface

1. Purpose

This article describes how to configure the Ethernet interface.
This article provides two ways to make it:

• via ifconfig: to put quickly and temporary the Ethernet interface with static IP address.
• via systemd: to change durably the Ethernet configuration with static IP address

2. Using Ifconfig tools

• Connect an Ethernet cable and enjoy

At startup SSH daemon (sshd) and ifplugd daemon are automatically launched:

• sshd (useful to perform ssh, scp)
• ifplugd detect:
  • udhcpc is launched on cable detection to retrieve an IP address,

If a DHCP server is not available, one can set the Ethernet IP adress with :

  ifconfig eth0 uuu.xxx.yyy.zzz

Warning

If there is some service such as systemd-networkd, NetworkManager, Connman , the configuration of Ethernet interface can change when the service see the change

To check if eth0 and the gateway are well configured, one can type:

 ifconfig
 route

In the console, a log similar to the one below should be displayed:

  ifconfig
 eth0      Link encap:Ethernet  HWaddr 00:80:E1:01:39:61  
           inet addr:10.48.1.172  Bcast:10.48.3.255  Mask:255.255.252.0
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           RX packets:18 errors:0 dropped:0 overruns:0 frame:0
           TX packets:2 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:1000 
           RX bytes:3038 (2.9 KiB)  TX bytes:684 (684.0 B)
           Interrupt:103 
 STM32MP1 # route
 Kernel IP routing table
 Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
 default         lme-gw-vl802.lm 0.0.0.0         UG    10     0        0 eth0
 10.48.0.0       *               255.255.252.0   U     0      0        0 eth0

3. Using systemd-networkd service

Systemd-networkd is a network service provided by systemd.

3.1. Ethernet interface

Systemd-networkd provides a directory on which the Ethernet interface must be configured via configuration file: /lib/systemd/network.

  ls /lib/systemd/network
50-wired.network            52-static.network.static    80-container-vz.network
50-wired.network.static     80-container-host0.network  99-default.link 
51-wireless.network.sample  80-container-ve.network

ST provide some configurations file:

• 50-wired.network: basic DHCP configuration for each ethX ethernet interface
• 50-wired.network.static: example of basic DHCP configuration on which eth0 are exclude of list
• 52-static.network.static: example of static IP configuration for eth0

3.2. Configuration file

Example of configuration:
DHCP configuration;

[Match]
Name=eth*

[Network]
DHCP=ipv4

Static IP configuration:

[Match]
Name=eth0

[Network]
DNS=192.168.72.254
Address=192.168.72.2/24
Gateway=192.168.72.254

[Match]

• MACAddress= a whitespace-separated list of hardware addresses
• Name= a white-space separated list of device names or expression (e.g. eth*).
• Host= the machine hostname

[NETWORK]
[Network]

• DHCP= enables the DHCP client, value can be: yes, no, ipv4, ipv6
• DHCPServer= enables the DHCP server for this configuration
• DNS= list DNS addresses in case of static configuration (you may specify several addresses)
• IPForward= configures IP packet forwarding, value can be: ipv4 or ipv6
• IPMasquerade= configures IP masquerading for the network interface. If enabled, packets forwarded from the network interface will be appear as coming from the local host. Takes a boolean argument. Implies IPForward=ipv4. Defaults to "no". Value can be yes or no.

All parameters are described on official documentation of systemd-networkd:

3.3. DHCP configuration

DHCP configuration;

[Match]
Name=eth*

[Network]
DHCP=ipv4

All Ethernet interface are configured with DHCP client address.

3.4. STATIC configuration

Static configuration;
Add a new file 52-static.network with the following content
(/lib/systemd/network/50-wired.network or /lib/systemd/network/52-static.network)

[Match]
Name=eth0

[Network]
DNS=192.168.72.254
Address=192.168.72.2/24
Gateway=192.168.72.254

Eth0 Ethernet interface are configured with static IP address.

Information

In case of static configuration or specific configuration, please take care to not configure two time your Ethernet interface , with the static configuration example you need to exclude eth0 interface of default configuration (here 50-wired.network)

Exclude eth0 from default Ethernet configuration:
Change the file 50-wired.network (or 80-wired.network) with the following content
(/lib/systemd/network/50-wired.network or /lib/systemd/network/80-wired.network)

[Match]
Name=eth[1-9]

[Network]
DHCP=ipv4

3.5. DHCP Server configuration

DHCP server example:

[Match]
Name=eth0

[Network]
Address=192.168.72.1/24
DHCPServer=yes
IPForward=ipv4
IPMasquerade=yes

Dynamic Host Configuration Protocol (See https://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol for more details)

uniprocessor

Receive

Transmit

Dynamic Host Configuration Protocol (See https://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol for more details)

uniprocessor

Receive

Transmit