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Difficulty: HardDNS Lookup and Name Resolution Roles in Enterprise Networks

An enterprise workstation is configured with a primary DNS server address of 10.10.20.5. The user attempts to access an external website by entering `service.partnercloud.com` into a web browser. The internal DNS server (10.10.20.5) is operational and has recursion enabled, but it currently has no cached record or authoritative zone file for `partnercloud.com`. Which statement accurately describes the name resolution role and process performed by the internal DNS server to resolve this request?

  1. The internal DNS server acts as a recursive resolver for the client, sending iterative queries to external root, TLD, and authoritative name servers on the client's behalf, and then returns the final IP address to the workstation.Answer
  2. B
    The internal DNS server returns a referral response to the workstation containing the IP address of a root DNS server, instructing the workstation to issue subsequent iterative queries directly over TCP port 53.
  3. C
    The internal DNS server broadcasts an ARP request across the local subnet to locate the default gateway for `partnercloud.com` before initiating a direct UDP name lookup.
  4. D
    The internal DNS server rejects the query and sends an ICMP Destination Unreachable message to the workstation because enterprise DNS servers only answer queries for locally hosted authoritative zones.

Answer

The internal DNS server acts as a recursive resolver for the client, issuing iterative queries to root, TLD, and authoritative DNS servers on behalf of the workstation, and returning the resolved IP address to the client.
In enterprise network operations, host computers act as stub resolvers that issue recursive queries to their designated internal DNS server. When the local DNS server lacks an authoritative zone or cached entry for a domain, it assumes the role of a recursive resolver: it queries external DNS servers (root hints, TLD servers, and domain authoritative servers) iteratively on behalf of the client and returns the resolved IP address back to the workstation.

Step-by-Step Solution

1
Identify the type of query originated by the client workstation.
The workstation sends a recursive DNS query to its configured local DNS server (10.10.20.5).
Standard client operating systems perform recursive lookups, delegating the entire resolution workflow to their designated local resolver.
2
Determine the local DNS server's cache and authoritative state.
The server has no cached entry and is not authoritative for `partnercloud.com`.
Because the answer is not cached or stored locally, the server must query external hierarchy nodes.
3
Trace the server-side lookup process.
The local server issues iterative queries starting at the DNS root servers, progressing to the TLD servers (.com), and finally querying the authoritative server for `partnercloud.com`.
Recursive resolvers execute iterative queries on behalf of the requesting host to obtain the final answer.
4
Complete the resolution back to the host.
The local DNS server caches the answer and sends an A record response containing the IP address to the workstation.
The client receives a single final answer directly from its local DNS server.

Key Concept

DNS Recursive vs. Iterative Query Roles in Enterprise Networks
Estimated Time:1m 30s
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Topics

DNS Lookup and Name Resolution Roles in Enterprise Networks

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