@Krishna M Welcome to the Microsoft Q&A Platform. Thank you for reaching out & I hope you are doing well. I understand that you would like to migrate from a legacy SKU to a Generation2 VpnGw4 I am afraid you will be required to delete this gateway and create a new VPN Gateway only, in this scenario. This is by design. The resizing of VpnGw SKUs is allowed within the same generation only.
Refer : Change to the new gateway SKUs
- There will be a downtime for this.
- You must plan a change window.
- This also means, you should create the individual 30 connections again.
With the said, you should focus on reducing the downtime for this.
- What can be done is that you can rely on Powershell to create the connections
- Refer : Create the VPN connection
- While you recreate the gateway - the IP Address will change. This means, you should configure the existing connected VPN devices to accept the S2S Connection from the new IP.
- What I would recommend is to deploy a dummyVPNgateway and try to establish a VPN Connection to the 30 connections.
- Once the connections are successful, you can proceed with deploying the desired SKU in the HubVnet.
Kindly let us know if this helps or you need further assistance on this issue. Thanks, Kapil