Internet service provider (ISP) redundancy allows you to define multiple links to two ISPs in order to provide a high-availability connection with failover capability to the Internet, or load balancing for outbound Internet traffic.

High availability mode allows you to designate a primary link over which all outbound Internet traffic will flow, and a backup link that activates automatically in the event that the first link fails.

Load-balancing mode allows you to direct outbound Internet traffic between two ISP links concurrently, and set the percentage of total Internet traffic per link. It also supports failover if one of the links should fail.

To enable ISP redundancy

  1. In the Forefront TMG Management console tree, click the Networking node.

  2. In the details pane, click the ISP Redundancy tab.

  3. On the Tasks tab, click Enable ISP Redundancy, and then follow the instructions in the wizard. Note the following:

    1. Each network must have a Network Address Translation (NAT) relationship with the External network.

    2. Static NAT rules take precedence over ISP redundancy configuration settings. This means that static NAT traffic directed to a specific ISP link is not rerouted if the link is down.

    3. When configuring load balancing, you can designate that traffic sent to a range of IP addresses is routed to a specific ISP link. To do so, click Explicit Route Destinations, and then click Add Range. You can add multiple ranges.

    4. After completing the wizard and clicking Apply on the Apply Changes bar, existing connections will continue over their current Internet link. The newly applied policy is relevant for new connections only.

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