Add network config suggestions for VM running Ubuntu

Signed-off-by: Chris Chiu <[email protected]>

Author: mingshuoqiu

docs/vm/backup-restore.md

@@ -58,6 +58,24 @@ The `State` will be set to `Ready` once the backup is complete.
 
 Users can either restore a new VM or replace an existing VM using this backup.
 
+:::note
+
+The network configuration of a virtual machine running an Ubuntu release later than 16.04 is likely managed by `netplan` by default. Before creating backups, you must stop the virtual machine, edit the configuration (**Edit Config > Advanced Options**), and then restart the virtual machine. Use the following `network` settings as reference for DHCP configuration.
+
+```YAML
+network:
+  ethernets:
+    enp1s0:
+      dhcp4: true
+      dhcp6: true
+      dhcp-identifier: mac
+  version: 2
+```
+
+The restored virtual machine retains the machine ID of the original virtual machine. If `dhcp-identifier: mac` is not specified, the restored virtual machine receives the same IP address from the DHCP server because `netplan` uses the machine ID as the DHCP client identifier by default. This is why you must configure the `network` settings before creating backups of virtual machines running Ubuntu. Failure to do so may result in unexpected behavior and potential network conflicts.
+
+:::
+
 ### Restore a new VM using a backup
 
 To restore a new VM from a backup, follow these steps:
@@ -174,6 +192,24 @@ The `State` will be set to `Ready` once the snapshot is complete.
 
 Users can either restore a new VM or replace an existing VM using this snapshot.
 
+:::note
+
+The network configuration of a virtual machine running an Ubuntu release later than 16.04 is likely managed by `netplan` by default. Before creating snapshots, you must stop the virtual machine, edit the configuration (**Edit Config > Advanced Options**), and then restart the virtual machine. Use the following `network` settings as reference for DHCP configuration.
+
+```YAML
+network:
+  ethernets:
+    enp1s0:
+      dhcp4: true
+      dhcp6: true
+      dhcp-identifier: mac
+  version: 2
+```
+
+The restored virtual machine retains the machine ID of the original virtual machine. If `dhcp-identifier: mac` is not specified, the restored virtual machine receives the same IP address from the DHCP server because `netplan` uses the machine ID as the DHCP client identifier by default. This is why you must configure the `network` settings before creating snapshot of virtual machines running Ubuntu. Failure to do so may result in unexpected behavior and potential network conflicts.
+
+:::
+
 ### Restore a new VM using a snapshot
 
 To restore a new VM from a snapshot, follow these steps:

docs/vm/create-vm.md

@@ -297,6 +297,24 @@ network:
 
 You can also use the `Advanced > Cloud Config Templates` feature to create a pre-defined cloud-init configuration template for the VM.
 
+:::note
+
+The network configuration of a virtual machine running an Ubuntu release later than 16.04 is likely managed by `netplan` by default. Please use the following `network` settings as reference for DHCP configuration to prevent IP address conflicts when restoring a virtual machine from a snapshot or backup.
+
+```YAML
+network:
+  ethernets:
+    enp1s0:
+      dhcp4: true
+      dhcp6: true
+      dhcp-identifier: mac
+  version: 2
+```
+
+If dhcp-identifier: mac is not specified, the restored virtual machine will receive the same IP address from the DHCP server. This happens because netplan defaults to using the machine ID as the DHCP client identifier. As a result, the restored virtual machine will receive the same IP address from the DHCP server and lead to IP address conflicts.
+
+:::
+
 #### Installing the QEMU guest agent
 The QEMU guest agent is a daemon that runs on the virtual machine instance and passes information to the host about the VM, users, file systems, and secondary networks.