After you add a property to a domain, the next step is to add traffic targets to the property. When you create traffic targets for a new or existing property, the available options vary depending on the property type.

1. Log in to ​Control Center​.

2. Go to ☰ > DNS SOLUTIONS > Global Traffic Management. The Traffic Management Domains page opens.

3. In the Domain column, click the domain name. The Properties page opens.

4. Click the property name to view its assigned Traffic Distribution Targets.

5. Click Add New Target. One data center is defined for each target up to the configured number of traffic targets defined in the load balanced property.

   If all data centers are assigned to a traffic target, a dialog box appears stating that there are no more data centers available for the new traffic target. Click Cancel to create a new data center by going to the Data Centers tab, or click OK to clone an existing data center.

6. Complete these options.

   • Balance All Targets Evenly. These property types have a Balance All Targets Evenly option you can select to distribute the weight equally among all the targets. Each target's Data Center Weight and Goal percentage changes accordingly.

     • Weighted Random Load Balancing
     • Weighted Random Load Balancing with Data Center Stickiness
     • Performance-Based Load Balancing
     • Performance-Based Load Balancing with Load Feedback (targets computed from version weights)
     • Performance-Based Load Balancing with Load Feedback Based on Liveness Test Download Scores (deprecated)

   • Mirror Failover property's Set as Primary option lets you specify one target as the primary data center/target. To change the existing primary target to a different target, click Set as Primary on the other target.

   • Data Center Weight. Use this to manually distribute the weight among the targets. Each target's goal percentage changes accordingly. Not all properties have this option.

   • Data Center. Specifies the target's data center. You can choose a data center from the menu, but if one is already in use a clone is used instead.

   • Servers. Specifies the IP addresses or hostnames of the servers. For hostnames that return IP addresses, all IP addresses are tested for liveness.

   • Handout CNAME. You can enter an optional handout CNAME for each data center. This defines the answer given if any endpoint in the selected target is available.

   • Backup Traffic Target. Serves as an alternate if all the other traffic targets are down.

   • Backup Answer. Enter the backup answer IP address or URL.

7. Click Add to Change List & Next. Some property types direct you to the Liveness Test page and others go to the Review page.

Computed targets

With XML load objects, the target load and capacity can be supplied in the load object (optional), as an XML load object can report just the current load. When you use non-XML load objects or download score based load balancing, only the current load is reported and GTM computes the target and capacity as follows.

• You configure each property with a traffic weight per data center. For example, for an even split between two data centers you might give each data center a weight of 1. GTM normalizes the two weights, splitting them evenly (0.5 and 0.5) across the data centers so they total 1.

• GTM collects the load information (either from load objects or from liveness test download scores) and sums the load across all data centers for a property. It then multiplies this sum by the load imbalance factor to get a total target load and computes each data center's target by multiplying the total target by the data center's normalized weight.

For example, if you have two data centers configured for an equal traffic split, and you are using download score based load balancing, and your load imbalance factor is 1.25, and data center A is reporting download times of 1 second while data center B is reporting download times of 4 seconds, then.

• The total load is 5.

• The total target load is 6.25 (5 * 1.25).

• The target load for each data center is 3.125 (half of 6.25).

This puts data center B over its target load and data center A under its target load, so GTM attempts to shift some traffic from data center B to data center A.

If you configure your property for Performance-Based Load Balancing with Load Feedback Based on Liveness Test Download Scores or Performance-Based Load Balancing with Load Feedback (targets computed from configured weights) , the computed-targets flag for your property is set automatically.

Backup target

You can optionally configure a property with a backup target. If GTM determines that all of the servers configured for your property are down, and you have configured a backup target, queries for the property return the backup target. If you have not configured a backup target, and all servers are down, GTM assumes that all servers are up. If all servers are down, GTM returns the IP addresses of the dead (down) servers so it does not return an empty answer.

Handout CNAMEs

In a property's configuration, you can optionally enter a handout CNAME for each data center. When you make a query for such a property, GTM determines to which data center you should be mapped. If that data center has a handout CNAME configured, the answer returned is the handout CNAME, rather than the servers that might be configured for the data center.

Handout CNAMEs are most often used with autonomous system (AS) maps, CIDR maps, and geographically mapped properties, but they can be used with any type of property.

Zero target

In performance load-feedback, non-load feedback, and weighted random load feedback you can set the target percentage for one or more data centers in a property to zero. GTM does not send any traffic to those data centers, except in the case where all the non-zero data centers are down: in that case, all traffic goes to whichever data centers are up, even if they have a zero target. As soon as a non-zero target data center is live again, the data centers with a zero target no longer receive traffic. If all data centers are down, including the zero target one, and there is no backup CNAME for the property, the zero target is reinstated and traffic is directed to the data center with non-zero targets.

If a datacenter is going offline for maintenance, we recommend that you check the Disabled box for that data center for the duration of the maintenance period, rather than setting its target to zero (0).

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The zero target is always applied strictly, meaning that even if the load imbalance factor is nonzero, GTM does not allow any traffic to go to the zero-target data center except under the conditions described above.

If you want to have a backup data center that always gets traffic, even when both it and the primary data centers are down, configure a failover property with that data center as its primary, and use this property as the backup CNAME for the main property.