It is a common occurrence for a router to receive self- originated link state advertisements via the flooding procedure. A self-originated advertisement is detected when either 1) the advertisement's Advertising Router is equal to the router's own Router ID or 2) the advertisement is a network links advertisement and its Link State ID is equal to one of the router's own IP interface addresses.
However, if the received self-originated advertisement is newer than the last instance that the router actually originated, the router must take special action. The reception of such an advertisement indicates that there are link state advertisements in the routing domain that were originated before the last time the router was restarted. In most cases, the router must then advance the advertisement's LS sequence number one past the received LS sequence number, and originate a new instance of the advertisement.
It may be the case the router no longer wishes to originate the received advertisement. Possible examples include: 1) the advertisement is a summary link or AS external link and the router no longer has an (advertisable) route to the destination, 2) the advertisement is a network links advertisement but the router is no longer Designated Router for the network or 3) the advertisement is a network links advertisement whose Link State ID is one of the router's own IP interface addresses but whose Advertising Router is not equal to the router's own Router ID (this latter case should be rare, and it indicates that the router's Router ID has changed since originating the advertisement). In all these cases, instead of updating the advertisement, the advertisement should be flushed from the routing domain by incrementing the received advertisement's LS age to MaxAge and reflooding (see Section 14.1).