Connection from azure to on prem not working after New external IP – Where to Update?

Question

Connection from azure to on prem not working after New external IP – Where to Update?

Aran Billen 976

Hi all,

We’ve recently switched our broadband lines, which means we now have a new external IP. This IP is used in several places, including Azure, where we run a site-to-site VPN from our on-premises server.

I updated the IP in the Local Network Gateway resource within Azure, but the VPN connection then broke.

My question is: does this need to be updated somewhere else on the Azure side (e.g., Virtual Network Gateway, Virtual Network), or could it be something within our firewall: Smoothwall, like a missing or misconfigured rule?

Just putting ideas out there, as I’m not sure what else I might be missing!

Ganesh Patapati 12,170 Reputation points Microsoft External Staff Moderator

2025-09-19T17:35:05.7733333+00:00
Hello Aran Billen

After updating the Local Network Gateway, ensure that the settings for your Virtual Network Gateway reflect the new IP as well. Sometimes this also needs to be verified to establish a successful VPN connection.

To resolve the problem, first try to reset the Azure VPN gateway and reset the tunnel from the on-premises VPN device. If the problem persists, follow these steps to identify the cause of the problem.

Prerequisite step

Check the type of the Azure VPN gateway.

Go to the Azure portal.

Go to the virtual network gateway for your VNet. On the Overview page, you see the Gateway type, VPN type, and gateway SKU.

Step 1: Check whether the on-premises VPN device is validated

Check whether you're using a validated VPN device and operating system version. If the device isn't a validated VPN device, you might have to contact the device manufacturer to see if there's a compatibility issue.

Make sure that the VPN device is correctly configured. For more information, see Edit device configuration samples.

Refer: https://learn.microsoft.com/en-us/answers/questions/4371232/site-to-site-vpn-connection-via-azure-vpn-gateway

Follow-Up Questions:

Have you updated the IP address in the Virtual Network Gateway settings as well?

Are there any specific error messages displayed in Azure when you check the VPN connection status?

Have you reviewed the firewall rules in Smoothwall to ensure they accommodate the new IP?

Is there a possibility that other configurations (like routing or NAT) could be affected by the IP change?

Can you confirm if all parts of the network (both Azure and on-premises) have been updated with the new IP?

I hope this was helpful!

If the above is unclear or you are unsure about something, please add a comment below.
Ganesh Patapati 12,170 Reputation points Microsoft External Staff Moderator

2025-09-22T12:07:43.62+00:00

Hello Aran Billen

Can you please update us if the action plan provided was helpful?

Should there be any follow-up questions or concerns, please let us know and we shall try to address them.
Aran Billen 976 Reputation points

2025-09-22T14:06:25.35+00:00

Hi,

Where in Virtual Network Gateway can I change the external IP?
Ganesh Patapati 12,170 Reputation points Microsoft External Staff Moderator

2025-09-23T19:48:24.7566667+00:00

Hello Aran Billen

Please let us know if you have tried all the steps mentioned above, and kindly share the requested details so we can continue troubleshooting.
Ganesh Patapati 12,170 Reputation points Microsoft External Staff Moderator

2025-09-26T11:46:55.3866667+00:00

Hello Aran Billen

Please let us know if you have tried all the steps mentioned above, and kindly share the requested details so we can continue troubleshooting.
Ganesh Patapati 12,170 Reputation points Microsoft External Staff Moderator

2025-09-26T18:22:59.1933333+00:00

Hello Aran Billen

Please let us know if you have tried all the steps mentioned above, and kindly share the requested details so we can continue troubleshooting.
Ganesh Patapati 12,170 Reputation points Microsoft External Staff Moderator

2025-09-29T20:23:02.2566667+00:00

Hello Aran Billen

Please let us know if you have tried all the steps mentioned above, and kindly share the requested details so we can continue troubleshooting.

Your answer

Ganesh Patapati 12,170 Reputation points Microsoft External Staff Moderator

2025-09-19T17:35:05.7733333+00:00

Hello Aran Billen

After updating the Local Network Gateway, ensure that the settings for your Virtual Network Gateway reflect the new IP as well. Sometimes this also needs to be verified to establish a successful VPN connection.

To resolve the problem, first try to reset the Azure VPN gateway and reset the tunnel from the on-premises VPN device. If the problem persists, follow these steps to identify the cause of the problem.

Prerequisite step

Check the type of the Azure VPN gateway.

Go to the Azure portal.

Go to the virtual network gateway for your VNet. On the Overview page, you see the Gateway type, VPN type, and gateway SKU.

Step 1: Check whether the on-premises VPN device is validated

Check whether you're using a validated VPN device and operating system version. If the device isn't a validated VPN device, you might have to contact the device manufacturer to see if there's a compatibility issue.

Make sure that the VPN device is correctly configured. For more information, see Edit device configuration samples.

Refer: https://learn.microsoft.com/en-us/answers/questions/4371232/site-to-site-vpn-connection-via-azure-vpn-gateway

Follow-Up Questions:

Have you updated the IP address in the Virtual Network Gateway settings as well?

Are there any specific error messages displayed in Azure when you check the VPN connection status?

Have you reviewed the firewall rules in Smoothwall to ensure they accommodate the new IP?

Is there a possibility that other configurations (like routing or NAT) could be affected by the IP change?

Can you confirm if all parts of the network (both Azure and on-premises) have been updated with the new IP?

I hope this was helpful!

If the above is unclear or you are unsure about something, please add a comment below.
Ganesh Patapati 12,170 Reputation points Microsoft External Staff Moderator

2025-09-22T12:07:43.62+00:00

Hello Aran Billen

Can you please update us if the action plan provided was helpful?

Should there be any follow-up questions or concerns, please let us know and we shall try to address them.
Aran Billen 976 Reputation points

2025-09-22T14:06:25.35+00:00

Hi,

Where in Virtual Network Gateway can I change the external IP?
Ganesh Patapati 12,170 Reputation points Microsoft External Staff Moderator

2025-09-23T19:48:24.7566667+00:00

Hello Aran Billen

Please let us know if you have tried all the steps mentioned above, and kindly share the requested details so we can continue troubleshooting.
Ganesh Patapati 12,170 Reputation points Microsoft External Staff Moderator

2025-09-26T11:46:55.3866667+00:00

Hello Aran Billen

Please let us know if you have tried all the steps mentioned above, and kindly share the requested details so we can continue troubleshooting.
Ganesh Patapati 12,170 Reputation points Microsoft External Staff Moderator

2025-09-26T18:22:59.1933333+00:00

Hello Aran Billen

Please let us know if you have tried all the steps mentioned above, and kindly share the requested details so we can continue troubleshooting.
Ganesh Patapati 12,170 Reputation points Microsoft External Staff Moderator

2025-09-29T20:23:02.2566667+00:00

Hello Aran Billen

Please let us know if you have tried all the steps mentioned above, and kindly share the requested details so we can continue troubleshooting.