Firewalls don’t usually break in production.

They break during implementation.
In real enterprise environments, most firewall incidents are not caused by bugs or attacks —
they’re caused by how we implement the design.
After working on multiple firewall implementations, here are some common anti-patterns I keep seeing:
🔹 Rules implemented before traffic is clearly understood
When flows aren’t mapped properly, implementation turns into trial-and-error.
🔹 Direct production changes without staged validation
No UAT, no shadow rules, no hit-count verification — just hope.
🔹 One firewall doing everything because it’s “already there”
Routing, NAT, IPS, VPN, east–west inspection — all forced into a single device.
🔹 Zones created based on IP ranges, not trust levels
This works initially, but collapses as applications scale and environments grow.
🔹 Temporary rules added during cutover — never removed
Six months later, no one remembers why they exist,
but everyone is afraid to delete them.
From an implementation engineer’s mindset, the goal is not:
❌ “Can I make this work today?”
The real implementation questions are:
✔ Can this be rolled back safely?
✔ Is the traffic observable before enforcement?
✔ Will another engineer understand this rule 6 months later?
Good implementation avoids outages.
Great implementation avoids future confusion.
Firewalls enforce policy.
Implementation decides whether that policy survives production.
➡️ In my next post, I’ll continue this series by breaking down
how an architect-style implementation approach
changes the way we design zones, enforce trust, and reduce firewall sprawl —
without adding complexity or buzzwords.