A failover context can be setup with the New configuration wizard or the Change configuration wizard.
After you setup a failover context by using the rtdr command, all other attributes used with the rtdr command can then take the primary Context ID. This provides an environment in which it appears as if you are dealing with one context, either in a primary or a failover mode. The underlying configurations are really two different, tightly related, contexts. You only need to remember the primary Context ID to failover, resync, and failback.