How long will secondary servers attempt to contact the primary server before considering the zone dead?

• A. One week
• B. One day
• C. One month
• D. One hour

Answer: (A)

Secondary DNS servers stay authoritative for a zone as long as they can reach the primary to refresh its data. The timer that determines when a non-contact period means the zone is no longer trusted is the expire value found in the SOA (Start of Authority) record. If the primary cannot be reached and updates cannot be received, the secondary will keep attempting according to the retry interval, but after the expire period elapses without successful contact, the zone is considered dead and the data on the secondary is no longer treated as authoritative.

One week is the typical default expire value used in many DNS implementations, meaning secondaries will continue serving the zone for about seven days without contact before giving up. The other durations shown would be much shorter lifetimes for the zone and are not the standard default, though they can be configured differently in some environments.