A high availability (HA) firewall is a system that ensures that the network is protected even if one of the firewall devices fails. Redundancy provides continuous security coverage and there is no single point of failure. This contrasts with single firewall setups that can lead to lengthy downtime when devices fail.

In this article, you will learn how high availability firewall systems work and the most important design options when implementing them. We will also introduce a few best practices to maximize the benefits from high availability architecture.

Key features of high-availability firewalls

Core features of High Availability firewalls include:

  • Redundant firewall devices: HA firewall systems have multiple firewall peers that work together to provide continuous protection. This is also known as HA clustering.
  • Automatic failover: If one firewall device fails, the system automatically switches to a secondary device. A seamless failover process ensures that the network is still protected. HA systems never have a single point of failure.
  • Load balancing: HA systems distribute network traffic across multiple firewalls. This optimizes performance and ensures that no single device becomes a bottleneck.
  • Stateful failover: HA firewall systems maintain the state of network connections. If one firewall goes offline, the new firewall device can pick up where the previous one left off.

Why do you need a high availability firewall?

HA firewalls deliver important benefits for corporate networks:

  • Improved protection: With HA firewall configuration in place, the network is protected at all times, even in the event of a device failure.

  • Better performance: HA firewall systems distribute network traffic, which can improve performance and prevent bottlenecks.

  • Reduced downtime: With automatic failover, the network experiences minimal downtime in case of a device failure.

These benefits also have many advantages for companies as a whole. Benefits of a robust HA firewall configuration include:

  • Avoiding reputational damage: Lengthy downtime and unreliable systems damage corporate reputations. Customers are likely to look elsewhere if payment portals or services are unavailable.
  • Meeting SLAs: Clients often sign SLAs when purchasing services. These agreements include demanding uptime requirements. HA firewalls help to achieve these targets.
  • Better customer relations: On a day-to-day level, HA firewalls improve the customer experience. This encourages increased revenues and higher return rates.
  • Enhanced data security: Firewalls are a critical part of data security architecture. Any downtime or unreliability can put confidential data at risk.

What is active/passive HA?

High Availability firewalls come in various node configurations (or clustering modes). This includes active/active and active/passive HA setups.

Active/Passive High Availability involves two devices: an active (or primary firewall) and a passive device. The active firewall handles network traffic and delivers network services. The passive component remains on standby. HA links are only activated if the active device fails.

Active/passive HA key points:

  • One device is active and handles the traffic. The other is passive and acts as a backup.
  • The passive device is only activated in the event of a failure of the active device.
  • The failover time is usually short.
  • The passive device is updated with the state of the active device via a heartbeat connection. This regularly updates the firewall state. HA links sure the passive firewall is ready to take over at any given moment.

What is N+1 redundancy for firewalls?

N+1 redundancy is a more secure form of active/active HA firewall configuration.

In active/active configurations, two or more devices operate at all times. Active devices share the network load. If a device fails, another active firewall can take up the slack and ensure constant protection.

In N+1 redundancy architecture, active devices are backed up by redundant firewall devices. If an active node fails, a passive firewall can take its place.

N+1 redundancy key points:

  • Provides additional protection against device failure.
  • Allows for automatic failover.
  • Maintains network uptime in all circumstances.
  • Requires one more device than the minimum necessary to handle expected traffic.

This level of redundancy is useful in large enterprise networks where the availability of the network is crucial.

N+1 architecture also allows for load balancing across all network nodes. Load balancing optimizes network performance and reduces the risk of excessive downtime.

Best practices to maintain high availability

High availability firewalls deliver important benefits. But HA systems must be implemented and maintained properly to maximize their effectiveness. Best practices for putting in place high availability network architecture include:

  1. Apply strategic redundancy design. HA firewalls should focus coverage on mission- critical assets. These are the apps and data containers used daily to deliver corporate services. Prioritize redundancy for critical workloads with the highest business value. Failure in these areas will have high costs for any business.

  2. Build failover into your network architecture. All HA configurations should include failover processes. This ensures that firewalls and other security tools remain online and effective during network outages. It also makes it easier to manage network traffic. If traffic flows fail in one part of the network, failover processes divert it to alternative active nodes.

  3. Think about geographic redundancy. Many companies maintain numerous active locations. Design HA systems that protect infrastructure if one local network goes down. Ensure firewall protection is available for all network users via active nodes.

  4. Leverage load balancing. Active/active or N+1 HA setups enable load balancing across the company network. Balance traffic loads to ensure seamless failover should an active node fail. Traffic should automatically flow from damaged firewall nodes to devices with active coverage. This creates an "insurance policy" for service apps by increasing fault tolerance levels.

  5. Sync your HA firewall with RPO objectives. Most companies operate a Recovery Point Objective (RPO) of 60 seconds or less. Configure your active firewalls and heartbeat connection settings to suit your chosen RPO. In the event of network failure, a low RPO minimizes data loss - a critical advantage of applying high availability systems.

Conclusion: are high availability firewalls right for your organization?

High availability firewalls are a good fit for companies that:

  • Rely on continuous uptime
  • Need to ensure constant data protection
  • Want to combine network security and load balancing
  • Have low risk tolerance

Companies fitting that profile may find that a high availability firewall is an essential component of their network security strategy. High availability ensures that the network is protected at all times and provides continuous uptime, even in the event of a device failure.

Thanks to automatic failover, load balancing, and stateful failover, an HA firewall can improve network performance and reduce downtime. Results include improved customer relations, stronger reputation management, and better network performance. Given those benefits, HA firewalls are often a sound network security investment.