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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 to define the hostname and port of a CDN's streaming media service endpoint?

    Answer: SRV

    SRV records specify both the hostname and TCP/UDP port for a specific service, enabling clients to discover service endpoints automatically.

  2. What happens to DNS resolution if all of a CDN domain's authoritative nameservers become unreachable simultaneously?

    Answer: DNS resolution fails; clients cannot reach the CDN until at least one nameserver recovers

    Without any reachable authoritative nameserver, recursive resolvers cannot obtain DNS answers and resolution fails entirely.

  3. A CDN operator wants to ensure that DNS queries from European users are answered by European PoPs. Which feature should be configured on the authoritative DNS?

    Answer: GeoDNS (geography-based DNS routing)

    GeoDNS inspects the requester's IP geolocation and returns records pointing to the nearest regional PoP.

  4. What is the role of glue records in DNS, and when are they required for a CDN's nameservers?

    Answer: They provide A records for nameservers within the same zone to break circular delegation dependencies

    Glue records are A records in the parent zone for in-bailiwick nameservers, preventing a chicken-and-egg resolution loop.

  5. Which protocol encrypts DNS queries between a client and resolver to prevent eavesdropping and manipulation?

    Answer: DNS over HTTPS (DoH) or DNS over TLS (DoT)

    DoH (port 443) and DoT (port 853) wrap DNS queries in TLS, providing confidentiality that DNSSEC alone cannot offer.

  6. What is the significance of the DNS 'minimum TTL' field in the SOA record for a CDN zone?

    Answer: It sets the caching duration for negative (NXDOMAIN/NODATA) responses from this zone

    Per RFC 2308, the SOA minimum TTL governs how long negative responses for names in that zone are cached by resolvers.

  7. A CDN customer configures www.example.com as a CNAME to edge.cdn-provider.net. The CDN provider's TTL on edge.cdn-provider.net is 60 seconds. The customer's TTL on the CNAME is 3600 seconds. How long will a resolver cache the final IP address?

    Answer: 60 seconds — the lowest TTL in the resolution chain governs the overall cache lifetime

    Resolvers must honor each record's own TTL; the shortest TTL encountered in the chain (60s on the A record) determines how soon the IP is re-queried.

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