Image by: Brett Sayles

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Why migrate from Cisco ASA to Fortinet FortiGate?

Did you know that 67% of enterprises using legacy firewalls experience higher operational costs due to complex management and limited security features? If you’re still running Cisco ASA firewalls, you’re likely facing challenges like:

• Outdated security architectures that can’t handle modern threats
• Limited visibility into encrypted traffic (ASA can’t inspect TLS 1.3)
• High TCO with separate licenses for VPN, IPS, and advanced features

Fortinet FortiGate offers:

This guide walks network engineers through the technical process of migrating from ASA to FortiGate while maintaining business continuity.

Pre-migration discovery phase: Laying the groundwork

A successful migration starts with comprehensive discovery. Follow this checklist:

1. ASA configuration audit

Run these CLI commands to document your current state:

show running-config
show route
show vpn-sessiondb detail
show asp table socket

2. Network topology mapping

• Create physical and logical diagrams of all security zones
• Document all interfaces (VLANs, IP assignments, speed/duplex)
• Identify traffic flows between zones

3. Policy and object inventory

Export these key elements:

1. ACL rules with service/port mappings
2. NAT rules (static, dynamic, PAT)
3. VPN configurations (site-to-site and remote access)
4. Custom objects (network groups, service definitions)

Using FortiConverter for automated policy translation

FortiConverter (official tool page) automates 80-90% of policy conversion:

Conversion workflow

1. Upload ASA config: Import your running-config or startup-config file
2. Policy mapping: The tool matches ASA rules to FortiOS constructs
3. Validation: Review flagged items needing manual intervention

What converts automatically

• Standard ACLs with permit/deny actions
• Network objects and service definitions
• Basic route statements
• Interface configurations

Common conversion challenges

These often require manual fixes:

“ASA’s object-group nesting doesn’t always map cleanly to FortiGate address groups. We typically see 15-20% of rules need tweaking after automated conversion.”

Manual validation for NAT rules and IPsec VPNs

Critical security elements require hands-on verification:

NAT rule migration

ASA’s NAT syntax differs significantly. Compare:

IPsec VPN considerations

Key differences to address:

• IKEv1 vs IKEv2 preference settings
• Phase 1/Phase 2 proposal parameters
• VPN tunnel interface binding

Pro tip: Use this VPN migration checklist to avoid common pitfalls.

Post-migration testing for zero-downtime cutovers

Follow this phased testing approach:

Lab validation

1. Test all policies in a non-production environment
2. Verify traffic flows match ASA behavior
3. Confirm VPN connectivity with partner sites

Parallel operation

During cutover:

• Run both firewalls in parallel using routing changes
• Monitor FortiGate logs for blocked traffic
• Have rollback procedures documented

Final verification

Check these post-cutover:

1. Application connectivity tests
2. Throughput benchmarks
3. Security policy hit counters

Conclusion

Migrating from Cisco ASA to Fortinet FortiGate delivers modern security capabilities while reducing operational complexity. By following this technical guide – from thorough discovery through automated conversion to rigorous testing – network engineers can execute seamless transitions. Remember to:

1. Document all ASA configurations before conversion
2. Validate NAT and VPN rules manually
3. Test extensively in parallel before cutover

For complex migrations, consider engaging Fortinet Professional Services or certified partners to ensure business continuity.

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