Default IPv6 router
If the switch receives RAs from a single IPv6 router on the same VLAN or subnet, the switch configures a global unicast address and selects the advertising router as the default IPv6 router.
If multiple IPv6 routers on a VLAN send RAs advertising the same network, the switch configures one global unicast address and selects one router as the default router, based on the router's relative reachability, using factors such as router priority and route cost.
If multiple IPv6 routers on a VLAN send RAs advertising different subnets, the switch configures a corresponding global unicast address for each RA and selects one of the routers as the default IPv6 router, based on route cost. When multiple RAs are received on a VLAN, the switch uses the router priority and route cost information included in the RAs to identify the default router for the VLAN.