Always On VPN Client Routes Missing

Choosing an Enterprise VPN

When configuring Always On VPN for Windows 10 and Windows 11 clients, administrators may encounter a scenario where an IPv4 route defined in Microsoft Endpoint Manager/Intune or custom XML is not reachable over an established Always On VPN connection. Further investigation indicates the route is added to the configuration on the endpoint but does not appear in the routing table when the connection is active.

Routing Configuration

When split tunneling is enabled, administrators must define routes to IP networks that are reachable over the Always On VPN connection. The method of defining these routes depends on the client configuration deployment method.

Endpoint Manager

Using Microsoft Endpoint Manager, administrators define IP routes in the Split Tunneling section of the configuration settings for the Always On VPN device configuration profile. Routes are defined by entering the destination prefix and prefix size. In this example, the 10.0.0.0/8 and 172.21.12.0/21 IPv4 networks are defined for routing over the Always On VPN tunnel.

Custom XML

Using custom XML deployed using Microsoft Endpoint Manager, System Center Configuration Manager (SCCM), or PowerShell, routes are defined in the XML file using the following syntax.

Client Configuration

Validate the routing configuration has been implemented on the endpoint successfully by running the following PowerShell command.

Get-VpnConnection -Name <Connection Name> | Select-Object -ExpandProperty Routes

As you can see here, the IPv4 routes 10.0.0.0/8 and 172.21.12.0/21 are included in the client’s Always On VPN configuration, as shown below.

Missing Route

However, after establishing an Always On VPN connection, the 172.21.12.0/21 network is not reachable. To continue troubleshooting, run the following PowerShell command to view the active routing table.

Get-NetRoute -AddressFamily IPv4

As you can see above, the only IPv4 route in the VPN configuration added to the routing table is the 10.0.0.0/8 network. The 172.21.12.0/21 IPv4 route is missing.

Network Prefix Definition

IPv4 routes missing from the Always On VPN client’s routing table result from incorrect network prefix definition. Specifically, the IPv4 route 172.21.12.0/21 used in the example here is not a valid network address. Rather, it is a host address in the 172.21.8.0/21 network, as shown below.

The Get-Subnet PowerShell cmdlet is part of the Subnet PowerShell module. To install this module, run the following PowerShell command.

Install-Module Subnet

Resolution

Using the example above, enabling access to the 172.21.12.0/21 subnet would require defining the IPv4 prefix in the routing configuration as 172.21.8.0/21. The moral of this story is always validate routing prefixes to ensure they are, in fact, network addresses and not host addresses.

Additional Information

Always On VPN Routing Configuration

Always On VPN Default Class-based Route and Microsoft Endpoint Manager/Intune

Always On VPN Windows 11 Issues with Intune

Always On VPN RasMan Errors in Windows 10 1903

Since the introduction of Windows 11, there have been numerous reports of issues with Always On VPN when deployed using Microsoft Endpoint Manager/Intune. Specifically, administrators have been reporting that Always On VPN profiles are being deleted, then later reappearing. Obviously, this is highly disruptive to users in the field.

Update January 25, 2022: Microsoft has released a fix for the issues described in this article. It is included with KB5008353 (build 22000.469).

Causes

According to Microsoft, there are several causes for deleted VPN profiles.

Changes to an Existing Profile

Missing Always On VPN profiles commonly occurs when updating settings for an existing VPN profile applied to Windows 11 endpoints. In this scenario, the VPN profile is deleted but not immediately replaced. Synchronize the device with Microsoft Endpoint Manager/Intune once more to return the VPN profile.

Multiple Profiles

Issues with Always On VPN profiles may also occur if two new VPN profiles are applied to the endpoint simultaneously.

Remove and Replace

Removing and replacing an Always On VPN profile at the same time will also result in connectivity issues.

Reference: https://docs.microsoft.com/en-us/mem/intune/configuration/vpn-settings-configure

Workaround

There is no known workaround for these issues at this time. Microsoft is aware of the problem and is working on a fix, and until then, rolling out Windows 11 with Always On VPN should be avoided.

Additional Issues

There have been reports of other known issues with Windows 11 and Always On VPN. For instance, my PowerShell script that removes an Always On VPN connection doesn’t work with Windows 11. I’m working to resolve that issue as we speak.

Are you experiencing any issues with Always On VPN on Windows 11? Please share them in the comments below!

Always On VPN Short Name Access Failure

Using Microsoft Endpoint Manager (Intune), administrators can provision Always On VPN to devices that are Azure AD joined only. Users accessing on-premises resources from these devices can still use seamless single sign-on, making this deployment option popular for organizations moving to the cloud.

Short Names

After deploying Always On VPN to Windows 10 devices that are Azure AD joined only and configured to use client certificate authentication, administrators may find that users cannot access on-premises resources by their short name, such as \\app1. The connection fails and returns the following error message.

“Windows can’t find <servername/sharename>. Check the spelling and try again.”

FQDN

Interestingly, on-premises resources are accessible using their fully qualified domain name (FQDN), such as \\app1.corp.example.net.

Troubleshooting

Testing name resolution using the short name works as expected, and the resource is reachable at the network layer, as shown here.

Workaround

This issue is related to how Windows performs authentication when connected via VPN. To resolve this issue, edit the rasphone.pbk file and change the value of UseRasCredentials to 0. Rasphone.pbk can be found in the $env:AppData\Microsoft\Network\Connections\Pbk folder.

After updating this setting, restart the VPN connection for the change to take effect.

Proactive Remediations

While helpful for testing, editing rasphone.pbk manually obviously does not scale well. To address this, consider using Intune Proactive Remediations. Intune Proactive Remediations allows administrators to deploy detection and remediation PowerShell scripts to monitor specific settings and update them if or when they change. Proactive Remediations will ensure the setting is applied consistently across all managed endpoints.

GitHub Repository

I have created a new GitHub repository dedicated to PowerShell scripts for Endpoint Manager Proactive Remediations for Always On VPN. There you will find detection and remediation scripts for the UseRasCredentials settings change described in this article.

Additional Information

Always On VPN Endpoint Manager Proactive Remediation Scripts on GitHub

Endpoint Manager Proactive Remediations Tutorial

%d bloggers like this: