Share via

Virtual network gateway keeps disconnecting

Stuart P 25 Reputation points
2025-07-23T10:32:53.05+00:00

Our virtual network gateway has started randomly disconnecting our physical offices from the vpn. This seems to have started since changing to standard public IP address. If I reset the gateway it brings the connections back up. Sometimes they will stay up for a day. Other times it disconnects again after a few minutes. Our routers are Draytek so not officially supported but they have worked like this for years.

Constantly resetting the connection isn't a viable long term solution. Would welcome any other steps I can try to resolve this.

Azure Virtual Network
Azure Virtual Network
An Azure networking service that is used to provision private networks and optionally to connect to on-premises datacenters.
Accepted answer
  1. Ganesh Patapati 8,755 Reputation points Microsoft External Staff Moderator
    2025-07-23T15:49:20.3866667+00:00

    Hello Stuart P

    In order to determine the exact cause, you can try to run a packet capture on Azure VPN which can help you get an idea if anything is causing this issue.

    You can follow this documentation to set-up a packet capture on Azure VPN gateway.

    1. Since your Draytek routers are not officially supported, ensure that you are having a validated devices per Azure’s compatibility guidelines. Check whether you are using a validated VPN device and operating system version. If the VPN device is not validated, you may have to contact the device manufacturer to see if there is any compatibility issue.
    2. Make sure that the VPN device is correctly configured. For more information, see Editing device configuration samples.
    3. Looks like the updated version (3.4.0.0) might be the reason for this issue. Please refer: https://learn.microsoft.com/en-us/azure/vpn-gateway/azure-vpn-client-versions#azure-vpn-client---windows
    4. The reason might be the current refresh token in the Azure VPN client, acquired from Entra ID, has expired or become invalid. This token is renewed approximately every hour. Entra tenant administrators can extend the sign-in frequency by adding conditional access policies. Please work with your Entra tenant administrators to extend the refresh token expiration interval. For your reference: https://learn.microsoft.com/en-us/azure/vpn-gateway/vpn-gateway-vpn-faq#vpn-disconnect
    5. Ensure that the keep-alive settings on your Draytek routers are configured correctly. Adjusting the keep-alive interval can help maintain the connection. For example, set the keep-alive interval to a lower value (e.g., 10 seconds) to ensure that the connection remains active.
    6. Make sure that the virtual network, subnets and, ranges in the Local network gateway definition in Microsoft Azure are same as the configuration on the on-premises VPN device. Also, Verify that the Security Association settings match.
    7. The virtual network gateway has limit of 200 subnet Security Association Limitations If the number of Azure virtual network subnets multiplied times by the number of local subnets is greater than 200, you might see sporadic subnets disconnecting.
    8. If the Internet facing IP address of the VPN device is included in the Local network gateway address space definition in Azure, you may experience sporadic disconnections.

    I hope this has been helpful!

    If the above is unclear or you are unsure about something, please add a comment below.

    0 comments

1 additional answer

Sort by: Most helpful
Most helpful Newest Oldest
  1. Stuart P 25 Reputation points
    2025-08-06T08:50:13.0933333+00:00

    VPN now seems to have stabilised. Seems there was a fault at the Azure end, with the Basic virtual network gateway SKU, which has been resolved.

    1 person found this answer helpful.
    0 comments

Your answer

Answers can be marked as Accepted Answers by the question author, which helps users to know the answer solved the author's problem.