You can set the router lifetime value in seconds for router advertisements on the IPv6 interface to 0 or from the configured maximum router advertisement interval to 9000 seconds. The router lifetime value specifies the usefulness of the router as a default router on this IPv6 interface. Configuring the lifetime to 0 specifies that the router should not be considered a default router for this interface. If the lifetime is set to a nonzero value, it can not be less than the configured maximum router advertisement interval.
This example sets the router lifetime value to 2200 seconds for VLAN 50:
System(su-config)->interface vlan 50 System(su-config-intf-vlan.0.50)->ipv6 nd ra lifetime 2200 System(su-config-intf-vlan.0.50)->