nerdexam
EC-Council

312-50V13 · Question #87

Under what conditions does a secondary name server request a zone transfer from a primary name server?

The correct answer is A. When a primary SOA is higher that a secondary SOA. A secondary name server requests a zone transfer from a primary name server when it detects that the primary's Start of Authority (SOA) record indicates a newer version of the zone data.

Submitted by chiamaka_o· Mar 6, 2026Footprinting and Reconnaissance

Question

Under what conditions does a secondary name server request a zone transfer from a primary name server?

Options

  • AWhen a primary SOA is higher that a secondary SOA
  • BWhen a secondary SOA is higher that a primary SOA
  • CWhen a primary name server has had its service restarted
  • DWhen a secondary name server has had its service restarted
  • EWhen the TTL falls to zero

How the community answered

(27 responses)
  • A
    93% (25)
  • C
    4% (1)
  • D
    4% (1)

Why each option

A secondary name server requests a zone transfer from a primary name server when it detects that the primary's Start of Authority (SOA) record indicates a newer version of the zone data.

AWhen a primary SOA is higher that a secondary SOACorrect

The SOA record contains a serial number that identifies the version of the zone. When a secondary name server queries the primary and finds the primary's SOA serial number is higher than its own, it indicates that changes have been made to the zone, prompting the secondary to request a zone transfer to synchronize the data.

BWhen a secondary SOA is higher that a primary SOA

If a secondary's SOA serial number is higher than the primary's, it implies the secondary might have newer data, which is an anomalous situation in a typical primary-secondary setup and would not trigger a transfer from the primary.

CWhen a primary name server has had its service restarted

While a primary name server restart might be followed by zone changes, the direct condition that triggers a secondary to request a transfer is the serial number difference in the SOA record, not the restart itself.

DWhen a secondary name server has had its service restarted

When a secondary name server restarts, it will check the primary's SOA record to determine if a zone transfer is needed, but the actual condition for the request is the primary having a higher SOA serial number, not just the restart.

EWhen the TTL falls to zero

The TTL (Time To Live) value applies to individual resource records and dictates how long clients should cache a record, it does not directly trigger zone transfers between DNS servers.

Concept tested: DNS zone transfer triggers (SOA serial)

Source: https://learn.microsoft.com/en-us/windows-server/networking/dns/deploy/zone-transfers

Topics

#zone transfer#secondary DNS#SOA record#DNS synchronization

Community Discussion

No community discussion yet for this question.

Full 312-50V13 Practice