Cloud config examples
https://cloudinit.readthedocs.io/en/latest/reference/examples.html

Network
https://cloudinit.readthedocs.io/en/latest/reference/network-config-format-v2.html

cloud-init.network-config: |
            network:
              version: 2
              ethernets:
                mgmt-dev:
                  mtu: 9000
                  addresses:
                    - 10.33.1.21/20
                  routes:
                    - to: 10.33.0.0/16
                      via: 10.33.1.1
                    - to: 10.8.0.0/22
                      via: 10.33.1.1
                    - to: 192.168.252.0/23
                      via: 10.33.1.1
                  nameservers:
                    addresses:
                      - 10.8.1.74
                      - 10.8.1.174
                    search:
                      - dev.example.com
                mgmt-public:
                  addresses:
                    - 10.0.1.100/24
                  gateway4: 10.0.1.1

V1