Configuring High Availability for 6rd Using 6rd Anycast

You configure 6rd Anycast by defining two service sets that use the same softwire rule in both service sets, just as you do when you configure load-balancing for 6rd. However, you do not configure ECMP, and as a result, the service PIC daemon (spd) installs two routes each for the softwire concentrator address and 6rd domain pointing to each service interface. The forwarding plane can select any route based on the priority, which is computed when the spd installs the routes. The priority is computed based on the FPC, PIC, slot numbers, and subunit number used on the sp- interface. Only one PIC is used based on the route priority, and that PIC gets all of the 6rd traffic. If the PIC goes down. the route pointing to it is also deleted and the forwarding plane automatically selects the alternate available PIC.

6rd Anycast is completely stateless. The spd installs the route and doesn’t run any state machine for the PIC. Because the routes are pre-installed and service sets are already on the PIC, there is no service delay if a failover occurs.