What Do You Do About Your VPN If Your Firewall’s Down?
And then — bam — your firewall is dead. The entire office panics. The VPN stutters, and then crashes. Your remote team begins to start spamming the chat with can’t connect messages. Sound familiar?
If it does, you’re not alone. I’ve been in this industry since the early ’90s and I’ve seen it all — from Slammer worm being an absolute nightmare because unpatched SQL servers were just everywhere to firewall failures creating total light outs. Recently I worked with three banks to migrate them to a zero-trust model, and when their firewalls failed during testing, the VPN pain was severe.
Why Your VPN Crashes When Your Firewalls Bust
- VPN sessions disconnect due to traffic blockage.
- Remote users can’t access unless you set up redundancy
- If quick fixes undermine defenses, security gaps emerge.
Fix it by:
- Configuring failover mechanisms in your firewall
- Deploying redundant VPN gateways (one of their features is redundancy, because one isn’t enough).
- Setting up out-of-band access for emergency admin control.
Problems with Firewall & VPN Connection
Firewalls and VPNs: firewall is like the chef, the VPN is a pass-through in the kitchen, a pass-through between the dining room and the kitchen, and the firewall determines who gets through; the VPN encrypts. They need each other. Removing the firewall suddenly leads to secure VPN tunnels unable to create or hold sessions.
I’ve had clients who call me in a panic:
- All of our remote staff just got kicked off.
- Critical systems are not accessible remotely!
- Is there a way to avoid the firewall choke point? (No, not safely.)
A VPN effectively tunnels your data through a secure channel to your corporate network.
- NAT traversal: Translating private IP addresses.
- Packet filtering — Allowing legitimate traffic through
- Logging & monitoring — Security visibility.
In that case, when your firewall keels over, the VPN usually goes with it — unless you’ve planned for redundancy. (Spoiler alert: Far from all companies have.)
How Hardware Firewalls Take Down VPNs
The cause? It’s usually one of these:
- The firewall was merely the endpoint of the only VPN. It collapses when the firewall does, if the VPN server depends on the firewall to authenticate and route.
- Default gateway dependencies. Many VPN setups use the firewall as the only configured path for encrypted traffic. Firewalls are a pathless panacea there—no firewall = no path = no VPN.
- NAT/PAT settings are down following firewall crash. NAT traversal is required for VPN clients. That means cutting access when a firewall goes down and IP mappings are jumbled.
- No failover in place. Single point of failure-worst phrase in IT security You’re toast if the firewall is a bottleneck for message, and there’s no backup appliance/router handling requests.
- Split tunnels with poor configurations. Some companies configure VPN clients to enable access to both internal and internet resources. When the firewall gets lost, routing can go haywire — causing all sorts of unpredictable failures.
The bottom line? A VPN is only as effective as your firewall uptime strategy.
Making Secure Connectivity Work
This is how you need to construct a firewall-failure resistant VPN architecture:
1. Use Redundant VPN Gateways
- Install VPN concentrators in a DMZ or on separate devices.
- Set up multiple VPN endpoints, and account for failover when one goes down and another takes over.
- E.g. One VPN server inside and failover tunnel (AWS VPN, Azure VPN Gateway) cloud based.
2. High Availability (HA) Firewall Failover Setup
- HA firewalls redirect to a secondary appliance when the primary firewall crashes.
- Deploy active/active or active/passive firewalls (Fortinet or Palo Alto or Sophos or Cisco ASA — pick your poison).
3. Set up a Headless Management Facility
- Always have a secondary management access method to bypass the firewall (via dedicated IPMI/BMC access, LTE backup uplink, or secondary ISP circuit).
- You don’t want to be locked out of your own infrastructure!
4. Configure an Alternate Internet Gateway for VPN Clients
You are forced to trust not just the VPN provider with your traffic but also the ISP/uplink you use to connect to the VPN, and if they go down, they go down.
A secondary internet link specifically for VPN access might save your day.
5. Embrace Cloud Based VPN Failover (Zero Trust is the Future Anyway)
- If your on-prem firewall goes down, cloud-managed VPNs (e.g., ZTNA solutions) can automatically redirect traffic.
- Use device-based authentication and multi-factor to spread reliance away from a single firewall bottleneck.
Synthetic Security Solutions for PJ Networks VPN
At PJ Networks we have designed such resilient VPN setups for banks, fintechs and enterprises that can take down its firewalls, and their remote access will still keep working. Here’s where we part ways with others:
- Bespoke redundancy per client — every client gets its own, bespoke multi-layered VPN security model: on-prem, in cloud, failover-ready.
- Zero-trust architecture: Zero-trust architecture: The ability to identify the user and then connect to resources, so if the firewall goes down, authentication doesn’t.
- Automatic failover: VPN traffic will find its way, no ifs, ands, or buts. We apply SD-WAN and resilient routing policies to make sure.
- Emergency response playbooks: Whenever we support an organization, they receive a VPN failure-response playbook to help minimize downtime if things go south.
And this isn’t just theoretical — we’ve seen firewalls fail in live money environments. We’re building VPN security layers that keep the businesses floating.
Conclusion
Look, breakouts of firewalls do occur. Hardware breaks. Configurations glitch. Network teams become overconfident.
But when your firewall dies your VPN does NOT have to die with it. If it does, you have to change your architecture.
Security is not only about fighting the threats — it’s about preserving access during the crisis. Because they will.
When your firewall dropped, if your VPN dropped, then you’re in borrowed time. Time to fix that.