Cloud/Network-Requirements

This is a placeholder page for the discussion of what the Cloud image (Base at first, Atomic to follow) requires from a networking stack on it's images.

- configure DHCP, renew dhcp leases - configure with cloud-init - configure with traditional RH-ecosystem ifcfg-eth0 file (log warnings for unsupported options)

Questions!

- Q: any need to support more than one interface? - Q: if single interface, should we standardize on "eth0"" - Q: dns configuration? - Q: support static IP (via cloud-init?)

Several use cases in EC2 involve instances with multiple network interfaces and occasionally multiple addresses on a single interface. I do not believe all of those need to be configured automatically, but it ought to remain possible for a user/script/etc to make network configuration changes that persist across reboots.

Work in progress
mhayden is doing some rambling on systemd-networkd here since maxamillion asked so nicely.

systemd-networkd use cases

Here are some sample use cases for systemd-networkd and example configurations.

Simple DHCP on a single interface

For an interface eth0, a single .network file is needed:

# cat /etc/systemd/network/eth0.network
[Match]
Name=eth0

[Network]
DHCP=yes

Static address on a single interface

For an interface eth0, a single .network file is needed:

# cat /etc/systemd/network/eth0.network
[Match]
Name=eth0

[Network]
Address=192.168.0.50/24
Address=2001:db8:dead:beef::/64

# These are optional but worth mentioning
DNS=8.8.8.8
DNS=8.8.4.4
NTP=pool.ntp.org

You can also split up the addresses into separate blocks:

# cat /etc/systemd/network/eth0.network
[Match]
Name=eth0

[Network]
DNS=8.8.8.8
DNS=8.8.4.4
NTP=pool.ntp.org

[Address]
Address=192.168.0.50/24

[Address]
Address=2001:db8:dead:beef::/64

Or add static routes:

# cat /etc/systemd/network/eth0.network
[Match]
Name=eth0

[Network]
DNS=8.8.8.8
DNS=8.8.4.4
NTP=pool.ntp.org

[Address]
Address=192.168.0.50/24

[Address]
Address=2001:db8:dead:beef::/64

[Route]
Destination=10.0.10.0/24
Gateway=192.168.50.1

[Route]
Destination=10.0.20.0/24
Gateway=192.168.50.1

Do DHCP on all network devices

You can use wildcards almost anywhere in the [Match] block. For example, this will cause systemd-networkd to do DHCP on all interfaces:

[Match]
Name=eth*

[Network]
DHCP=yes

Bridging

Let's consider an example where we have eth0 and we want to add it to a bridge. This could be handy for servers where you want to build containers or virtual machines and attach them to the network bridge.

Start by setting up our bridge interface, br0:

# cat /etc/systemd/network/br0.netdev
[NetDev]
Name=br0
Kind=bridge

Now that we have a bridge device, let's configure the network for the bridge:

# cat /etc/systemd/network/br0.network
[Match]
Name=br0

[Network]
IPForward=yes
DHCP=yes

The IPForward=yes will take care of the sysctl forwarding setting for us (net.ipv4.conf.br0.forwarding = 1) automatically when the interface comes up.

Now, let's take the ethernet adapter and add it to the bridge:

# cat /etc/systemd/network/eth0.network
[Match]
Name=eth0

[Network]
Bridge=br0

Simply reboot the system and it will come up with eth0 as a port on br0.

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