Firewall Upgrade Mistakes
Introduction
It’s 9:15 AM, third cup of coffee going strong (yes, I measure my mornings by the coffee) and I’m sitting at my desk thinking about firewall OS upgrades — the double-edged sword of every network admin’s world. As someone who’s been at this (networking career) since 1993 as a network admin — dragging in anything from multiplexors for voice and data over the PSTN to tangling with the Slammer worm in person — I’ve seen my share of upgrade scar tissue. And let me tell you, nothing is as nerve-wracking as a failed firewall OS upgrade in a production banking environment. Lately, I have assisted three banks with rebuilding their zero-trust architectures, the tales I could tell of upgrade mishaps! So let’s get the show on the road — my short list of the most frequent firewall OS upgrade screw-ups, and much more importantly, what you can do about them.
Common Mistakes
First off, this is the thing with firewall OS upgrades: it’s not just whack an Update button in the GUI and go make yourself a cuppa while the unit magics itself rebooted into a safer future. Nope. These are the sentinels of your network; if they misbehave, your castle is wide open.
- Configurations/Setups not being backed up or Baselines
And you would think this is cybersecurity upgrade 101, but this sort of thing is still shockingly common. I saw one instance, this would have been the early 2000s an entire firewall config lost because an upgrade attempt went south – without backup. It was like seeing your car engine explode on the highway with not a spare part in sight. - No Compatibility Checks
What are they supposed to do, slap a shiny new OS on old hardware? Recipe for disaster. Or worst case – different firmware and software. In many cases, teams don’t even check the compatibility matrix at all, which is similar to putting diesel in a petrol car. Doesn’t work well. - Bad Timing and No Maintenance Window
The next is upgrading critical firewalls during peak hours or times when downtime hadn’t been shared with the stakeholders. I’ve been there. Networks dragged, users screamed, and the finger-pointing began. - Skipping Pre-Upgrade Testing
One of the biggest causes of upgrade failures is not doing your testing before upgrading. Testing an upgrade in the lab is not always an option folks take into account, or don’t even think is a best practice. I know — time pressure — but skipping this is like skipping a pre-flight inspection. - Not Having a Backup and Rollback Plan
What if the upgrade goes south — how do you roll back? Nobody likes to acknowledge it, but everyone has been caught flat-footed with no fallback plan. - Ignoring Post-Upgrade Validation
The upgrade isn’t complete once the firewall has rebooted. You must verify policy, logging, throughput, and connectivity. No validation = no legit upgrade. - Underestimating the Impact on Zero Trust Architectures
This one comes straight out of the bank stuff I have been working on recently. There are a lot of gratuitous opportunistic changes which are not trivial for zero trust policy enforcement and are a huge nope. - Blind Faith in AI-Enabled Upgrade Assistants
Personal rant here — I’m extremely skeptical about AI-powered tools that promise smooth upgrades. In my experience, most still need human guidance. You wouldn’t just pass keys over to a robot without a safety net.
Our Best Practices
Look, mistakes are cool — I’m far from the scoldy type, — I just want you to learn from my scars.
- Backup As If Your Job Depended On It (Because It Does)
Any advice? Every time before an upgrade: Backup configs, back up current firewall states, and take a snapshot. If possible, keep backups like these both on and off premises. - Not Optional: Compatibility Checks
Check release notes, HCLs and vendor advisories. Lebron 17 ‘Graffiti’ is now available at retailers. - Plan for Down Time and Communicate
Think of upgrades as a pit stop during a high-speed race. Announce your maintenace window early and get your Business units in. - Create a Development/Staging Environment
Recreate your firewall environment as much as possible and perform the the upgrade on it first. I say this constantly — a little here saves hours of down-time. - Have a Rollback Plan Prepared and Tested
That’s having the knowledge of how to reload previous configs, firmware or if necessary, swap hardware. Practice makes perfect. - Run the Post-Upgrade Validation Checks
Check:- Firewall policies
- Network throughput
- Log generation and alerts
Compatibility with SIEM and other monitoring systems
Ensure no important rules are missing or have had unexpected changes. - Record Everything – No Matter How Small
You (and your teammates) will thank you for this when troubleshooting. - Factor in Zero Trust Effect
On zero-trust policies, small changes have far-reaching effects. Ensure that identity enforcement, micro-segmentation, and access policies still work the way they should. - Human in the Loop — Always
You shouldn’t trust in summarization only. Have experienced eyes watching the upgrades, analyzing the logs and configs, and ready to step in if needed. - 48 hrs Post-Upgrade Monitoring as a Minimum
I know sometimes things come up even hours or days later. Keep a close eye.
Quick Take
- Backup first and foremost Do this before touching anything. Seriously.
- Test like hell in a sandbox environment.
- Communicate and plan in off-hours.
- Specify your rollback and use it when appropriate.
- Keep in mind that zero trust policies can fail quietly.
- You can’t rely blindly on AI tools for this.
- Post-upgrade monitoring — the fun’s not done.
Conclusion
There is something almost poetic about firewall OS upgrades — a mix of anticipation, dread and ultimate relief. From when I cut my teeth working with the early networking mux gear of the PSTN era to today, building and running PJ Networks and assisting customers like banks uplevel their security postures with zero-trust architectures, the same lessons apply. Preparation, testing, communication and validation are your top pals on this pursuit.
Funny thing is that I still get a bit of an adrenaline rush after all these years, clicking that upgrade button. Perhaps it’s the hacker in me (or perhaps it’s just caffeine). Either way, I think telling my story can spare you the same headaches.
Think of your firewall as the moat surrounding your cyberkingdom. Don’t let it become a leaky pipe because of an upgrade.
Back up your configs, plan your upgrades like a pro pit crew, and never trust your life to the vagaries of modern firewall architecture, particularly when zero-trust is involved. And if you’re not sure, well … you know who to call.
Sanjay Seth
CJ Networks Pvt Ltd
Cybersecurity Consultant
PS: Be careful out there. Hackers are always watching.