The first nameserver in /etc/resolv.conf is unreachable, and every lookup on the host stalls for five seconds before the second server answers. Which resolv.conf directive shortens that per-server wait?

LPIC-1 Exam 102-500, objective 109. Networking fundamentals hard

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The options

Correct options timeout:1

Correct. timeout sets how long the resolver waits for a reply from one name server before it moves on and retries; the default is five seconds.

Not correct options attempts:1

Wrong. attempts caps how many times the resolver cycles through the whole server list. Cutting it reduces the number of rounds but leaves each individual wait at the full timeout.

Not correct options rotate

Wrong. rotate makes the resolver round-robin over the listed servers between queries to spread load. Some queries would still start on the dead server and wait out the timeout.

Not correct options ndots:1

Wrong. ndots sets how many dots a name must contain before it is tried as absolute rather than being appended to the search list. It affects how many queries are sent, not how long each one waits.

Why

The glibc resolver's stall on a dead server is governed by two independent numbers: timeout, the seconds spent waiting on a single server before giving up on that try, and attempts, the number of passes made over the whole nameserver list. Lowering timeout is what shortens each individual wait; lowering attempts only reduces how often you pay it. Both are capped internally, timeout at 30 seconds and attempts at 5, and the true remedy for an unreachable resolver is to remove it from the list.

Where this comes from

Cited
manual page resolv.conf(5)

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