A client workstation requests the IP address for an external hostname (app.sub.example.com) that is not in any local DNS cache. Arrange the steps of the recursive DNS lookup process in the correct order from initial query to final response.
- 1The client workstation sends a recursive DNS query for app.sub.example.com to its configured local DNS resolver.
- 2The local DNS resolver queries a DNS root name server to find the authoritative server for the .com top-level domain (TLD).
- 3The local DNS resolver queries the .com TLD name server to obtain the authoritative name server for example.com.
- 4The local DNS resolver queries the authoritative name server for example.com to obtain the host A record for app.sub.example.com.
- 5The local DNS resolver caches the IP address and returns the final resolution result to the requesting client workstation.
Answer
The correct sequence for recursive DNS resolution is: 1) Client sends recursive query to local resolver, 2) Resolver queries root server for .com TLD, 3) Resolver queries .com TLD server for example.com authoritative server, 4) Resolver queries authoritative server for app.sub.example.com host record, 5) Resolver caches the record and returns the IP address to the client.
The correct order follows standard hierarchical DNS resolution: the client workstation issues a recursive request to its local configured resolver. When the resolver's cache is clear, it queries a root name server to find the TLD server, then queries the .com TLD server to locate the authoritative server for example.com, and finally queries the authoritative server for the specific A record before caching and returning the answer to the client.
Step-by-Step Solution
Key Concept
Iterative and Recursive DNS Name Resolution Hierarchy