Network configuration in Photon OS

Photon instances are usually meant to be configured automatically with Cloud-config, this includes hostname, network settings, additional packages, etc. However there are some corner cases where you may need to manually configure an static IP address, like a Lightwave domain controller or a DNS server.

Static addressing configuration

By default in Photon OS DHCP comes enabled for all present network interfaces. This is more than enough for testing however for more permanent services like a Lightwave server is desirable to use static IP addresses.

If you are used to work with Red Hat or any of its variants your first move will be to look at /etc/sysconfig/network-scripts/ however there is nothing there, actually the path does not even exists. In Photon the network subsystem is controlled by systemd-networkd.

root@lightwave02 [ /etc/systemd/network ]# cat 10-dhcp-en.network
[Match]
Name=*

[Network]
DHCP=yes
root@lightwave02 [ /etc/systemd/network ]#

Drop a unit file in /etc/systemd/network to configure static IP address for a certain interface. Remove the unit file used for DHCP, name the file 10-static-en.network and include the following content.

[Match]
Name=eno1

[Network]
Address=192.168.161.21/24
Gateway=192.168.161.2
DNS=192.168.161.9

The [Match] section defines the network interfaces the configruation will be applied to, in this case eno1, and the [Network] section the configuration itself.

To apply the new settings restart systemd-networkd service.

systemctl restart systemd-networkd

Multi-protocol configuration

If you need to configure static IP for one interface and leave DHCP for the rest create two unit files:

• 10-static-en.network
• 20-dhcp-en.network

In the first one include a configuration similar to the one described before and for the second one use the following DHCP unit file.

[Match]
Name=en*

[Network]
DHCP=yes˚

Static routes

To configure static routes, in the file 10-static-en.network add any additional static routing information under the [Route] section.

[Route]
Gateway=192.168.161.10
Destination=172.16.10.0/24

Bond interfaces

Using networkd unit file we can create and configure a bond interface to provide load balancing and redundancy to the network connectivity within our Photon OS instance.

First remove any DHCP related unit file. And create three new files:

• 10-en.network
• 20-bond.netdev
• 30-bond-static.network

10-en.network will indicate networkd to put our eno interfaces under bond0.

[Match]
Name=eno*

[Network]
Bond=bond0

20-bond.netdev defines the behavior of the bond0 interface.

[NetDev]
Name=bond0
Kind=bond

[Bond]
Mode=balance-rr
MIIMonitorSec=10s

The section [NetDev] defines the name and kind of the network device and [Bond] defines de mode, by default balance-rr and MIIMonitorSec the interval of seconds for the link monitoring operation.

Finally 30-bond-static.network stores the IP configuration for bond0.

[Match]
Name=bond0

[Network]
Address=192.168.161.22/24
Gateway=192.168.161.2
DNS=192.168.161.6

I recommend to review systemd-networkd official documentation to get more details about the different options available. Stay tuned for more Photon content in future posts. And of course comments are welcome.

– Juanma