Which is a common DNS issue that can affect reachability?

Which is a common DNS issue that can affect reachability?

• A. Stale records
• B. IP address conflicts
• C. DHCP lease expiration
• D. Spanning tree loops

Answer: (A)

DNS reachability suffers when cached DNS entries become stale. If a hostname’s IP address changes but the resolver still holds an old A/AAAA record in its cache, queries can resolve to the wrong address or fail altogether, making the service appear unreachable. The impact is tied to how DNS caches responses and respects TTLs, so stale records linger until the cache refreshes. Keeping DNS records accurate, setting appropriate TTLs, and triggering cache refreshes or dynamic updates helps avoid these problems. Other options describe problems not driven by DNS itself: an IP address conflict disrupts general network operation by confusing devices on the same network; DHCP lease expiration affects IP assignment rather than DNS resolution directly; spanning tree loops cause layer-2 topology issues that can bring down multiple paths and overwhelm the network.

DNS reachability suffers when cached DNS entries become stale. If a hostname’s IP address changes but the resolver still holds an old A/AAAA record in its cache, queries can resolve to the wrong address or fail altogether, making the service appear unreachable. The impact is tied to how DNS caches responses and respects TTLs, so stale records linger until the cache refreshes. Keeping DNS records accurate, setting appropriate TTLs, and triggering cache refreshes or dynamic updates helps avoid these problems.

Other options describe problems not driven by DNS itself: an IP address conflict disrupts general network operation by confusing devices on the same network; DHCP lease expiration affects IP assignment rather than DNS resolution directly; spanning tree loops cause layer-2 topology issues that can bring down multiple paths and overwhelm the network.