Enterprise VPN Troubleshooting for Developers
A practical guide to diagnosing and resolving VPN connectivity issues in development environments. Learn how enterprise VPNs interact with WSL, Docker, and virtual machines.
Few things derail developer productivity faster than VPN connectivity issues. You're connected to the corporate VPN, Windows applications work fine, but your Docker containers can't pull images, your WSL environment can't reach internal Git repositories, and you're staring at cryptic "No route to host" errors. Sound familiar?
Enterprise VPNs add layers of complexity that consumer VPNs don't have—split tunnelingSplit Tunneling🔐A VPN feature allowing some traffic through the VPN while other traffic uses your regular connection. policies, DNS configuration, certificate authentication, and integration with corporate security tools. When these intersect with development tools like WSL 2, Docker, and Hyper-V virtual machines, troubleshooting becomes a multi-layered puzzle.
This guide provides a systematic approach to diagnosing and resolving VPN connectivity issues in development environments. Whether you're dealing with Cisco Secure Client (AnyConnect), OpenVPNOpenVPN🔐An open-source VPN protocol widely considered secure and reliable, though slower than WireGuard., GlobalProtect, or Microsoft DirectAccess, the troubleshooting principles remain consistent.
How Enterprise VPNs Work
Before diving into troubleshooting, it's essential to understand what happens when you connect to a corporate VPN. This knowledge helps you identify where problems might occur.
The Connection Process
When you initiate a VPN connection, several things happen in sequence:
Split Tunneling vs Full Tunneling
Enterprise VPNs typically operate in one of two modes:
Full tunneling routes ALL your network traffic through the VPN, regardless of destination. This provides maximum security but can be slower for non-corporate resources and may cause issues with local network devices like printers.
Split tunneling only routes traffic destined for corporate networks through the VPN. Traffic to public internet destinations goes directly through your normal internet connection. This is more efficient but requires careful configuration to ensure security policies are maintained.
Your organization's choice between these modes significantly impacts how virtualization tools interact with the VPN. Split tunneling generally causes fewer issues with WSL and Docker, while full tunneling requires more careful network configuration.
VPN Compatibility with Virtualization Technologies
Modern development environments often involve multiple layers of virtualization. Understanding how VPNs interact with each layer is crucial for effective troubleshooting.
WSL 2 and VPN Challenges
WSL 2 runs a Linux kernel inside a lightweight Hyper-V virtual machine, as explained in our What is Windows Subsystem for Linux (WSL)? guide. This architecture creates networking complexity because WSL 2 has its own virtual network adapter that must somehow access the VPN tunnel established on the Windows host.
By default, WSL 2 uses NAT (Network Address Translation) networking. The WSL VM gets a private IP addressIP Address🔐A unique numerical identifier assigned to every device connected to the internet. (typically in the 172.x.x.x range), and traffic is translated through the Windows host. When a VPN is connected, this NAT traffic must be correctly routed through the VPN tunnel—and this is where things often break.
Common WSL 2 + VPN symptoms:
A recent Windows 11 bug affecting WSL mirrored networking and VPNs is documented in our news article: Windows 11 Updates Breaking Enterprise VPN Connections in WSL. If you're experiencing issues after October 2025 updates, this may be the cause.
Docker Desktop and VPN Interactions
Docker Desktop on Windows can run in two modes: WSL 2 backend (recommended) or Hyper-V backend. Both present VPN challenges, but for different reasons.
With the WSL 2 backend, Docker inherits all the WSL 2 networking complexities described above. Additionally, Docker creates its own virtual networks for container communication, adding another layer of routing complexity.
Docker-specific VPN issues include:
Hyper-V Virtual Machines
Traditional Hyper-V VMs have different networking options that affect VPN connectivity. The most common configurations are External Switch (bridged to physical adapter), Internal Switch (host-only network), and Default Switch (NAT with internet access).
When using an External Switch with a VPN, the VM may not receive VPN-routed traffic because the VPN tunnel is established on the host, not on the bridged network. Internal and Default switches generally work better with VPNs but may require additional routing configuration.
Diagnosing "No Route to Host" Errors
The infamous "No route to host" error indicates that your system cannot find a network path to the destination. This is one of the most common VPN-related errors in development environments. Let's systematically diagnose it.
Step 1: Verify Basic Connectivity
First, establish a baseline. From your Windows host (not WSL or a VM), test connectivity to the target resource:
ping internal-server.corp.example.com
If this fails on Windows, the problem is with your VPN connection itself, not virtualization. Check that your VPN client shows as connected and contact your IT department if basic connectivity fails.
If Windows works but WSL/Docker doesn't, you've confirmed the issue is with how virtualization tools access the VPN tunnel. Continue to the next steps.
Step 2: Check Route Tables
Network routing is often the culprit. Examine the routing tables to understand how traffic is being directed.
On Windows (PowerShell):
route print
On WSL/Linux:
ip route show
Look for routes to your corporate network ranges (e.g., 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16). In WSL, you should see routes pointing to a gateway. If the routes are missing or pointing to the wrong interface, that's your problem.
Step 3: Examine DNS Resolution
DNS issues masquerade as routing problems. Test DNS resolution separately from connectivity:
nslookup internal-server.corp.example.com
If DNS fails but you can ping the IP address directly, the issue is DNS configuration, not routing. Check which DNS servers your system is using:
On Windows:
ipconfig /all | findstr "DNS"
On WSL:
cat /etc/resolv.conf
WSL may be using different DNS servers than Windows. If WSL's resolv.conf points to a local address like 127.0.0.53, it's using systemd-resolved, which should inherit Windows DNS. If it points to something else, you may need to configure it manually.
Step 4: Test ARP Resolution
Address Resolution Protocol (ARP) maps IP addresses to MAC addresses on local networks. ARP failures prevent any communication, even when routes are correct.
arp -a
If you see incomplete ARP entries for your VPN gateway or target hosts, ARP requests aren't being answered. This is the root cause of the recent Windows 11 WSL/VPN bug—the VPN virtual adapter stops responding to ARP requests from WSL.
Step 5: Trace the Path
Use traceroute to see where packets are going (or stopping):
On Windows:
tracert internal-server.corp.example.com
On WSL/Linux:
traceroute internal-server.corp.example.com
If traceroute shows packets leaving through your regular internet gateway instead of the VPN interface, routing is misconfigured. If packets reach the VPN gateway but stop there, the VPN server may be blocking or not forwarding traffic from your virtualized environment.
Common Solutions and Workarounds
Fixing WSL 2 VPN Connectivity
Try these solutions in order:
1. Switch WSL networking modes
If you're using mirrored mode (networkingMode=mirrored in .wslconfig), try switching to NAT mode by removing that setting. If you're on NAT mode, try mirrored mode. Different VPN clients work better with different modes.
2. Manually configure DNS
If DNS is the issue, you can manually configure WSL to use your corporate DNS servers. Edit /etc/wsl.conf in your distribution:
[network]
generateResolvConf = false
Then create /etc/resolv.conf manually with your corporate DNS servers and restart WSL.
3. Add manual routes
If routing is the issue, you can add routes manually. First, find your VPN's gateway IP on Windows, then add a route in WSL:
sudo ip route add 10.0.0.0/8 via
Fixing Docker VPN Connectivity
Docker-specific solutions:
1. Configure Docker DNS
In Docker Desktop settings, you can specify custom DNS servers. Add your corporate DNS servers to ensure containers can resolve internal hostnames.
2. Use host networking for troubleshooting
Run containers with --network host to bypass Docker's network isolation temporarily. If this works, the issue is with Docker's network configuration, not the VPN itself.
3. Build with network access
For build-time network issues, ensure your Dockerfile doesn't rely on internal resources during build, or build on a system with direct network access.
Working with Your IT Department
VPN issues often require collaboration with your IT or network security team. Here's how to have productive conversations:
Information to Gather
Before contacting IT, collect:
Questions to Ask IT
Preventing Future Issues
Proactive steps to minimize VPN headaches:
Summary
VPN troubleshooting in development environments requires understanding multiple interconnected systems: the VPN client, Windows networking, virtualization layers, and your development tools. When "No route to host" errors appear, systematic diagnosis—checking connectivity, routes, DNS, and ARP—usually reveals the culprit.
Key takeaways:
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