Server Load Balancing

DrayTek Vigor 2960 and Vigor 3900 routers offer advanced load balancing features to spread usage across multiple interfaces and servers.

Server Load Balancing distributes load for incoming connections, providing redundancy and allowing the workload of these connections to be distributed among multiple servers.

Incoming connections for services such as websites or FTP (File Transfer Protocol) can be shared between multiple local servers connected to the DrayTek Vigor router's network, with up to 10 servers per load balancing group.

This can be useful in scenarios where it's desirable to have multiple servers perform the same task, if heavy usage (CPU usage or memory requirements) or many concurrent connections from clients could exceed the capabilities of a single server.

Balancing load in this way also reduces the risk of the internal server becoming a single point of failure; should one server become unresponsive, the router would send incoming connections to the remaining servers in the load balancing group.

Server Load Balance operates in a similar way to Port Forwarding, which receives a request on an external TCP or UDP port on the router, then forwards that connection to the internal server using NAT (Network Address Translation). With Server Load Balance, it is possible to utilise a single external network port for multiple internal servers.

Controlling Load Balance Distribution

When a connection request is received by the router, it is assigned to an available server, with requests assigned based upon the Weight value specified for each server, which is calculated as a ratio.

For example, if two servers are set up in a Server Load Balance group, with the first server's Weight set to 1, the second server's Weight set to 2; out of every 3 connection requests from clients, 1 is assigned to the first server and 2 are assigned to the second server.

Applicable Products:

The Server Load Balance feature is located in the [NAT] > [Server Load Balance] menu of the router's web interface.

This feature is supported on the Vigor 2960 and Vigor 3900 routers with the 1.3.0 firmware. Prior firmware versions do not support the Server Load Balance facility.