Renaming VLANs in a Mist switch template can cause port profiles configured directly at the switch level to lose their VLAN references. As a result, affected interfaces may revert to the default VLAN, potentially causing widespread network connectivity issues. This behavior is expected when switch-level port profiles reference VLAN names that are modified in the template.

• VLAN names were modified in a Mist switch template.
• Multiple switches experienced connectivity loss after the template change.
• Port profiles previously assigned to specific VLANs reverted to the default VLAN.
• Access switches received the new VLAN names, while referenced configurations were not updated automatically.
• Rollback attempts from the switch failed or generated rollback errors.
• Devices became unmanaged or temporarily lost connectivity following the template update.

For example:

 1- Applied the TEST port profile to ge-0/0/2:

2- Test port profile is using VLAN-12 and VLAN-16:

3- You can see VLANs 12 and 16 are coming from the template:

4- In this case the template is called "Test":

5- Then I changed the names on the template and Saved:

6- The following error shows up on the switch:

7 - Lastly, the port profiles defaults back to default VLAN for data and VoIP:

The issue was reproduced and validated in a lab environment.

When VLAN names are changed in a template, port profiles configured at the switch level do not automatically update their VLAN references. The port profiles continue referencing the original VLAN names, causing the configuration to fall back to the default VLAN

Recommendations:

• Reconfigure affected switch-level port profiles to reference the updated VLAN names.
• Use template-level or site-level port profiles whenever possible so VLAN reference changes are inherited automatically from the template.
• Avoid renaming VLANs that are currently referenced by switch-level port profiles without first updating the dependent configurations.
• Validate port profile assignments after making template VLAN modifications to prevent unintended VLAN fallback behavior.