Suppose that the command netstat -a hangs for a long time without producing output. You might suspect:

Question

Options

• AA problem with NFS.
• BA problem with DNS.
• CA problem with NIS.
• DA problem with routing.
• EThat the netstat daemon has crashed.

• A
  3% (1)
• B
  83% (24)
• C
  10% (3)
• E
  3% (1)

Explanation

netstat -a lists all active network connections and their states, and to do this it performs reverse DNS lookups on each IP address to display hostnames. If DNS is unavailable or slow to respond, netstat blocks on those lookups and appears to hang - it's waiting for name resolution that never comes back promptly.

Why the distractors are wrong:

• A (NFS): NFS problems affect file system mounts, not name resolution; netstat wouldn't hang waiting on NFS.
• C (NIS): NIS (Network Information Service) distributes config like /etc/passwd, not hostname resolution - a NIS outage wouldn't typically stall reverse lookups.
• D (Routing): A routing problem would cause connection failures, not cause a local diagnostic tool like netstat to hang silently.
• E (netstat daemon): netstat is a command-line tool, not a daemon - there is no "netstat daemon" to crash.

Memory tip: Think of it as "netstat is being nosy about names" - whenever a tool tries to convert IPs to human-readable hostnames and stalls, suspect DNS. Any command that hangs resolving names (not connecting) = DNS first.

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