On an OSPF network, routers learn routing information on the entire network by exchanging LSAs. Which of the following values is the LS Age in the LSA header when an LSA is deleted?

Question

Options

• A1800s
• B3600s
• C3000s
• D600s

• A
  6% (2)
• B
  76% (26)
• C
  3% (1)
• D
  15% (5)

Explanation

In OSPF, the MaxAge value is defined as 3600 seconds (1 hour), and when a router wants to flush or delete an LSA from the network, it sets the LS Age field to this MaxAge value (3600s) and refloors it. All receiving routers recognize a MaxAge LSA as expired and remove it from their link-state databases, effectively purging the entry network-wide. Option A (1800s) is the LSRefreshTime - the interval at which routers proactively re-originate their own LSAs to prevent them from expiring, not the deletion signal. Option C (3000s) is not a defined standard OSPF timer and serves no specific role in LSA lifecycle management. Option D (600s) is also not a recognized OSPF deletion value and would be confused with other shorter operational timers.

Memory tip: Think "3600 = gone" - one full hour (3600 seconds) is OSPF's way of saying an LSA has lived its maximum life. MaxAge equals MaxAge, and 3600 seconds is one hour, which is easy to anchor since it mirrors a common "session timeout" mental model.

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