Fault Tolerance

A Traffic IP address is an IP address that must remain highly available. You assign Traffic IP addresses to Traffic IP groups, and each group is managed by some of (or all of) the Traffic Managers in your cluster. A Traffic IP group contains either a single Traffic IP address (for EC2-Classic configurations) or one or more Traffic IP addresses (for VPC configurations).

In Figure, a Traffic IP group has been configured, spanning 3 of the 4 Traffic Managers in the cluster. These Traffic Managers ensure that any Traffic IP address assigned to the group is always available. If multiple addresses are assigned to the group, each is raised on a different Traffic Manager, distributed as evenly as possible.

For example, a web service might be published on IP address 34.56.78.90. You can ensure that the service is always available by adding this IP address to a Traffic IP group. The Traffic Manager cluster raises this IP address and manage all of the traffic to it. You typically configure the DNS entry for your service to resolve to one or more Traffic IP addresses, although you must use a VPC where more than one address is used.

All traffic destined for a particular Traffic IP address is handled by the Traffic Manager with the raised address. Any other Traffic Managers in the group run as hot spares, ready to take over if the active machine fails.

Each Traffic Manager reports periodically to the other Traffic Managers. If the Traffic Manager currently hosting the Traffic IP address fails, one of the remaining Traffic Managers takes over its share of traffic. In this way, services that depend on the Traffic IP addresses are always available.