Practice Test Geeks(CDN) Content Delivery Network Certification Practice Test
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DNS & Domain Management Flashcards

7 cards from real CDN practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 DNS & Domain Management flashcards as text

  1. Which DNS record type is used by CDNs to publish SPF policy when the CDN sends email on behalf of a customer domain?

    Answer: TXT

    SPF policies are stored in TXT records and list authorized mail-sending IP ranges, including those used by CDN-hosted email services.

  2. What is the purpose of a CAA (Certification Authority Authorization) DNS record in a CDN deployment?

    Answer: It restricts which certificate authorities may issue TLS certificates for the domain

    CAA records prevent unauthorized CAs from issuing certificates for your domain, reducing TLS hijacking risk.

  3. During a CDN failover, a TTL of 30 seconds on the primary A record was set in advance. What is the maximum time a client could still reach the failed origin after the DNS update?

    Answer: 30 seconds

    Clients cache DNS responses for the duration of the TTL, so a 30-second TTL means at most 30 seconds before the new record is fetched.

  4. What is DNS anycast and why do CDNs use it?

    Answer: Multiple servers share the same IP; BGP routes users to the topologically nearest one

    Anycast assigns identical IPs to multiple PoPs; BGP ensures each user's query reaches the geographically or topologically closest PoP.

  5. A CDN customer's subdomain media.example.com must be decommissioned, but its CNAME still points to the CDN edge. What security risk does this create?

    Answer: Subdomain takeover — an attacker can claim the CDN hostname and serve content under media.example.com

    If the CDN hostname is released and an attacker re-registers it, the dangling CNAME lets them hijack the subdomain.

  6. Which DNS resolution mode does a CDN's authoritative DNS use to direct mobile users to edge nodes with lower latency?

    Answer: ECS (EDNS Client Subnet) — passes client IP prefix to authoritative for geo-aware responses

    EDNS Client Subnet (ECS) allows the recursive resolver to share the client's IP prefix so the CDN's authoritative DNS can return geo-optimized records.

  7. What is negative caching in DNS, and how does it affect CDN traffic routing after a configuration error?

    Answer: NXDOMAIN/NODATA responses are cached for the SOA negative TTL, delaying recovery after fixing the error

    When DNS returns NXDOMAIN or NODATA, resolvers cache that negative result for the SOA's minimum TTL, so even after fixing the record, clients may be denied temporarily.

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