🚨 A common Palo Alto firewall mistake I still see in production

 

“Security policy is correct, but traffic still fails.”
This is one of the most frequent issues I troubleshoot during real customer implementations.

Let me explain why this happens 👇
🔍 The real problem
Many engineers focus only on Security Policies, but forget how Palo Alto actually processes traffic.

Palo Alto is zone-based, not interface-based.
So traffic evaluation depends on:
Source Zone
Destination Zone
Correct routing
NAT (if applicable)

Security policy order
If any one of these is wrong → traffic drops, even if the rule looks correct.
🧠 Real-world scenario
Trust → Untrust rule is present
Application is allowed
Service is correct

But traffic still fails because:
❌ Wrong zone mapping on interface
❌ Route points to different interface
❌ NAT rule hits before expected policy

Result?
📛 Packet hits interzone-default deny
✅ How I validate during implementation

My usual checklist:
Confirm interface → zone binding
Verify routing table for destination
Check NAT rule order
Match traffic using traffic logs
Use policy hit count, not assumptions

🎯 Key takeaway
👉 Palo Alto firewalls don’t fail because of missing rules
👉 They fail because of incorrect design thinking
Think like an architect, not just a rule creator.
If you’re implementing or troubleshooting Palo Alto in production, this mindset saves hours.