CompTIA Network+ Practice Test

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How long does a device cache a DNS lookup based on TTL?

For 60 seconds
For the specified TTL seconds
Indefinitely
For 30 minutes

The correct answer is: For the specified TTL seconds

The time-to-live (TTL) value in the context of DNS (Domain Name System) indicates how long a DNS resolver or caching server should retain a DNS record before querying the authoritative DNS server again. When a DNS lookup is performed, the record returned includes a TTL value, which represents the duration in seconds that the information can be cached. Thus, a device will cache a DNS lookup for the exact duration specified by the TTL value associated with that query. For example, if a DNS record has a TTL of 300 seconds, the device will hold that DNS record in its cache for 300 seconds before it removes the record and needs to perform a new DNS query. This mechanism is essential as it helps reduce DNS traffic and speeds up subsequent queries for the same domain by avoiding repeated lookups within the TTL period. The other options don't accurately reflect this caching behavior. Caching for a fixed time like 60 seconds or 30 minutes would not account for the variability of the TTL, which can be set by the DNS administrator. Caching indefinitely contradicts the purpose of TTL, as it would not allow for the updating of records when they change. Hence, the correct understanding of DNS caching is rooted in the specified TTL seconds provided by the DNS record