Document network support for configdrive

Author: vishesh92

source/adminguide/networking/dns_and_dhcp.rst

@@ -17,6 +17,13 @@
 DNS and DHCP
 ------------
 
-The Virtual Router provides DNS and DHCP services to the guests. It
-proxies DNS requests to the DNS server configured on the Availability
-Zone.
+The Virtual Router & ConfigDrive (since Apache CloudStack 4.20) provides
+DNS and DHCP services to the guests. It proxies DNS requests to the DNS
+server configured on the Availability Zone.
+
+.. note::
+   In case of a network with ConfigDrive, adding/removing nic to/from an
+   instance or updating the ip address of a nic will not be reflected in the
+   instance if the instance is already running. To do so, run
+   `cloud-init clean --machine-id -s` to clean the machine id and seed data.
+   Then reboot the instance to apply the changes.

source/adminguide/templates/_cloud_init.rst

@@ -215,6 +215,21 @@ These features can be implemented in `“Linux Template creation process” <_cr
 
    Cloud-init can parse and execute user-data form Cloud-stack during Instance creation. This feature works as is without additional configuration.
 
+#. **Network configuration with ConfigDrive**
+
+    Cloud-init can fetch network configuration from ConfigDrive. To enable this,
+    ensure network configuration is not disabled in cloud-init configuration.
+    
+    .. code:: bash
+
+      echo -e "\nnetwork: {}" >> /etc/cloud/cloud.cfg
+
+    .. note::
+      Adding/removing nic to/from an instance or updating the ip address of a nic
+      will not be reflected in the instance if the instance is already running. To
+      do so, run `cloud-init clean --machine-id -s` to clean the machine id and
+      seed data. Then reboot the instance to apply the changes.
+
 #. **Cleanup**
 
    Once desired cloud-init features are implemented, clean cloud-init tracker files.