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Configuring WAN Load Balancing

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If your network is prone to congestion, for example in large offices which include multiple active clients and/or servers, you can increase the amount of available bandwidth by configuring WAN load balancing. By default, the UTM-1 appliance routes all traffic to the primary Internet connection, and the secondary Internet connection is used only when the primary connection is down, or when a routing rule specifically states that traffic should be sent through the secondary connection. WAN load balancing automatically distributes traffic between the primary and secondary connections, allowing you to use both connections in parallel.

When one IP address sends packets to another IP address, the UTM-1 appliance examines each Internet connection's recent bandwidth utilization in kilobits per second to determine its load. The UTM-1 appliance then enters the source-destination pair in a load balancing table and specifies the least-loaded Internet connection as the connection to use for traffic between this pair. To prevent disruption of stateful protocols, the UTM-1 appliance will route all traffic between this pair to the specified Internet connection, so long as the pair remains in the load balancing table.

Note: By default, load balancing is performed when the amount of bandwidth utilization exceeds a threshold of 64 kilobits per second. You can change this threshold via the CLI. For information, refer to the Embedded NGX CLI Guide.

Note: By default, a source-destination pair is removed from the load balancing table after 1 hour of inactivity. You can change the default value via the CLI. For information, refer to the Embedded NGX CLI Guide.

Note: In order for WAN load balancing to be effective, there must be more than one active source-destination pair.

By default, the load distribution between Internet connections is symmetric; however, you can configure non-symmetric load balancing by assigning a different load balancing weight to each Internet connection. For example, if you assign the primary connection a weight of 100, and you assign the secondary connection a weight of 50, the UTM-1 appliance will only route traffic to the secondary connection if the primary connection's current load is more than twice the secondary connection's current load. Therefore, to ensure full utilization of both Internet connections, the ratio between the connections' load balancing weights should reflect the ratio between the connections' bandwidths.

Note: To ensure continuous Internet connectivity, if one of the Internet connections fails, all traffic will be routed to the other connection.

To configure WAN load balancing

  1. Configure the desired load balancing weight for both the primary and secondary Internet connections.

    For further information, see the Load Balancing Weight field in Using Internet Setup.

  2. Click Network in the main menu, and click the Internet tab.

    The Internet page appears.

  3. In the WAN Load Balancing area, drag the load balancing lever to On.

    WAN load balancing is enabled. Traffic will be distributed automatically across the defined Internet connections, according to the configured load balancing weights.

    Note: You can view the effect of WAN load balancing in the Traffic Monitor.

See Also

Configuring the Internet Connection


Using the Internet Wizard

Using Internet Setup

Setting Up Dialup Modems

Viewing Internet Connection Information

Enabling/Disabling the Internet Connection

Using Quick Internet Connection/Disconnection

Configuring a Backup Internet Connection