show ip ospf statistics

Provides information about how frequently a router is executing the SFP algorithm.This command also shows when the SPF algorithm last ran and is recommended as the first troubleshooting step for link-state advertisement (LSA) flapping.

Record of reasons causing SPF to be executed:

• N—A change in a network LSA (type 2) has occurred.
• R—A change in a router LSA (type 1) has occurred.
• SA—A change in a Summary autonomous system boundary router (ASBR) (SA) LSA has occurred.
• SN—A change in a Summary Network (SN) LSA has occurred.
• X—A change in an External Type-7 (X7) LSA has occurred.

CCNP-TSHOOT 642-832 Official Certification Guide and http://www.cisco.com/en/US/docs/ios/12_3t/ip_route/command/reference/ip2_s4gt.html#wp1167148