🔥 Why your firewall allows traffic… but users still see timeouts

Ever faced this?
✅ Security policy allows traffic
✅ NAT looks correct
✅ Routes are present
❌ Still applications fail / ping shows RTO
Most engineers stop troubleshooting at policy level.
That’s where the real problem starts.

🧠 The hidden culprit: Asymmetric routing
In many enterprise networks:
Forward traffic goes via Firewall A
Return traffic comes via Firewall B
Especially common during:
Multi-ISP setups
HA failover
Cloud ↔ On-prem connectivity

👉 Palo Alto firewalls are stateful
If the return packet doesn’t hit the same firewall/session → packet drop, even if policy allows it.

🔍 Common places this happens
Default route with path monitoring
ECMP without session synchronization
NAT pools not tied to interfaces
Cloud routing not aligned with firewall zones

✅ How architects prevent this
✔ Enforce symmetric routing
✔ Use proper HA design & session sync
✔ Bind NAT IPs to correct egress interfaces
✔ Validate routing from both directions, not just forward flow

💡 Architect mindset vs Engineer mindset
Engineer: “Policy is allowed, firewall issue”
Architect: “Where will the return packet land?”
That single question saves hours of troubleshooting.
If this helped you, 👍 or comment “ASYMMETRY”
More real-world Palo Alto & network design insights coming 🚀