What is the difference between multi-active and active-passive architecture?

In multi-active, all nodes handle traffic simultaneously, improving resource utilization and smoother failover. In active-passive, standby nodes are idle, causing potential switchover delays.

How to detect node failure?

Through health checks such as ICMP Ping, TCP port probes, or HTTP status code detection, periodically verifying node availability.

How does client-side smart switching work?

The client embeds a node list and performs real-time speed tests (e.g., latency, packet loss) to select the best node, with automatic failover support.

Load Balancing and Failover in VPN Services: High-Availability Connection Design with Multi-Active Architecture

7/7/2026 · 2 min

1. Overview of Multi-Active Architecture

In VPN service (often referred to as "airport") environments, a multi-active architecture means multiple nodes handle user traffic simultaneously, unlike traditional active-passive setups. This design improves resource utilization and enables true failover: when one node fails, traffic is automatically redirected to other active nodes with minimal user disruption.

2. Core Load Balancing Mechanisms

2.1 Intelligent DNS Resolution

Using GeoDNS or latency-based DNS, users are directed to the nearest available node. For example, a user in China might receive the IP of a Hong Kong or Japan node with the lowest latency.

2.2 Layer 4/Layer 7 Load Balancing

Layer 4: Based on IP and port forwarding (e.g., LVS, HAProxy), high performance for large UDP/TCP traffic.
Layer 7: Based on application protocols (e.g., HTTP/HTTPS), enabling content routing (e.g., Nginx, Traefik) for fine-grained control.

2.3 Session Persistence and Consistent Hashing

For protocols requiring connection state (e.g., SSH, gaming), consistent hashing ensures the same user's requests always go to the same node, preventing session interruption.

3. Failover Strategies

3.1 Health Checks

Nodes send periodic heartbeats (e.g., ICMP Ping, TCP port probes). If a node becomes unresponsive, it is immediately removed from the load pool. Typical intervals are 5-10 seconds with a 3-second timeout.

3.2 Automatic Switchover and Fallback

When the primary node fails, the client or ingress gateway automatically switches to a backup node. The process should include retry mechanisms and jitter to avoid thundering herd problems. After recovery, traffic can smoothly fall back, but stability must be ensured.

3.3 Multi-Region Redundancy

Nodes deployed in different geographic regions back each other up. For instance, using nodes in Japan, Singapore, and the US West Coast; when the Asia-Pacific network fluctuates, traffic is automatically routed to US nodes.

4. Practical Configuration Tips

Use BGP Anycast: Multiple nodes share the same IP via Anycast, routing user traffic to the nearest available node automatically, achieving network-layer high availability.
Client-Side Smart Switching: Embed a multi-node list in the client with real-time speed testing to automatically select the best node. For example, Clash Meta's url-test policy group.
Monitoring and Alerting: Deploy Prometheus + Grafana to monitor node latency, packet loss, and CPU load, with alert thresholds set.

5. Conclusion

Load balancing and failover under a multi-active architecture are critical for stable VPN service. By leveraging intelligent DNS, health checks, and multi-region redundancy, user experience can be significantly improved. In practice, balance performance and cost, and continuously optimize strategies.