There was a ospf route flap, which each route existed only several seconds not exceeding 15 seconds, and then the same route didn't disappare , but route age took account at 0 second again . I used command show ip ospf and I found that SPF algorithm times did not increased correspondly . My customer complained they feeled slow ,in fact there was lost packet . All these happened after I moved a parallel E1 from inter area ( area 0---area 1) to intra area ( only in area 1),that means I only change area boundary .