When configuring pfSense as a DHCP server, you have two primary options: ISC DHCP (the traditional choice) and KEA DHCP (a modern alternative). Both serve the same fundamental purpose—dynamic IP address assignment—but they differ in architecture, features, and performance.

This blog post compares KEA DHCP and ISC DHCP to help you decide which is best for your pfSense deployment.

• ISC DHCP: The Traditional Workhorse
  • Pros of ISC DHCP
  • Cons of ISC DHCP
• KEA DHCP: The Next Generation
  • Pros of KEA DHCP
  • Cons of KEA DHCP
• Which One Should You Use?
  • Use ISC DHCP if:
  • Use KEA DHCP if:
• Conclusion

ISC DHCP: The Traditional Workhorse

ISC DHCP (Internet Systems Consortium DHCP) has been the default DHCP server for pfSense for many years. It’s widely used and well-supported, but it has some limitations.

Pros of ISC DHCP

✔ Mature and Stable – Decades of development and widespread adoption.
✔ Deep pfSense Integration – Works seamlessly with pfSense’s web interface.
✔ Supports DHCP Failover – Can be set up for load balancing and redundancy.
✔ Static Mappings & Custom Options – Easily configure static leases, PXE boot, and option overrides.

Cons of ISC DHCP

❌ Single-Threaded – Performance bottlenecks under heavy loads.
❌ Configuration Reloads Disrupt Service – Any configuration change requires a restart, momentarily dropping active leases.
❌ End of Life in Sight – ISC is phasing out support for ISC DHCP in favor of KEA DHCP.

KEA DHCP: The Next Generation

KEA DHCP is the modern replacement for ISC DHCP, offering a more scalable and flexible solution. It is actively developed by the Internet Systems Consortium (ISC) and is expected to fully replace ISC DHCP in the future.

Pros of KEA DHCP

✔ Multi-Threaded Performance – Handles higher loads more efficiently.
✔ Live Configuration Changes – No need to restart the service when modifying settings.
✔ Database Support – Stores lease data in MySQL, PostgreSQL, or Cassandra, making it easier to manage in large environments.
✔ High Availability via Hooks – Supports customizable HA setups beyond traditional failover.
✔ REST API for Automation – Enables dynamic, API-driven DHCP configurations.

Cons of KEA DHCP

❌ Limited pfSense Integration – As of now, pfSense does not fully support KEA DHCP through the web UI.
❌ More Complex Configuration – Requires JSON-based configurations instead of traditional text files.
❌ Some Advanced Features Require Paid Hooks – Features like failover and lease reservation hooks require a support subscription from ISC.

Which One Should You Use?

Use ISC DHCP if:

• You want full pfSense web UI integration.
• You need simple DHCP management with traditional features.
• You rely on pfSense’s built-in failover and static mappings.

Use KEA DHCP if:

• You need higher performance in large environments.
• You prefer database-backed DHCP management.
• You require real-time configuration changes without service interruptions.
• You want API-based automation for dynamic networks.

For most pfSense users, ISC DHCP is still the best choice due to ease of configuration and full web UI support. However, as KEA DHCP matures, it will likely become the default DHCP solution for pfSense in the future.

Conclusion

While ISC DHCP remains the default choice for pfSense due to its simplicity and tight integration, KEA DHCP offers significant advantages in performance, scalability, and automation. If you manage a large network or require dynamic configurations, KEA might be worth the extra setup effort.

For now, pfSense users should stick with ISC DHCP, but keep an eye on future updates as KEA DHCP continues to gain support. Eventually, pfSense will likely transition fully to KEA DHCP as ISC DHCP reaches end-of-life.

📝 For more information about this DHCP transition within pfSense, please review this netgate forum discussion.