14.1. Premature aging of advertisements

A link state advertisement can be flushed from the routing domain by setting its LS age to MaxAge and reflooding the advertisement. This procedure follows the same course as flushing an advertisement whose LS age has naturally reached the value MaxAge (see Section 14). In particular, the MaxAge advertisement is removed from the router's link state database as soon as a) it is no longer contained on any neighbor Link state retransmission lists and b) none of the router's neighbors are in states Exchange or Loading. We call the setting of an advertisement's LS age to MaxAge premature aging. Premature aging is used when it is time for a self-originated advertisement's sequence number field to wrap. At this point, the current advertisement instance (having LS sequence number of 0x7fffffff) must be prematurely aged and flushed from the routing domain before a new instance with sequence number 0x80000001 can be originated. See Section 12.1.6 for more information.

Premature aging can also be used when, for example, one of the router's previously advertised external routes is no longer reachable. In this circumstance, the router can flush its external advertisement from the routing domain via premature aging. This procedure is preferable to the alternative, which is to originate a new advertisement for the destination specifying a metric of LSInfinity. Premature aging is also be used when unexpectedly receiving self-originated advertisements during the flooding procedure (see Section 13.4).

A router may only prematurely age its own self-originated link state advertisements. The router may not prematurely age advertisements that have been originated by other routers. An advertisement is considered self-originated 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.