A network technician is troubleshooting an issue where a dual-stack client workstation fails to connect to an internal host named `app-server.corp.local` over IPv6. The technician runs `nslookup -type=AAAA app-server.corp.local` and receives a response stating that the domain name does not exist. However, executing `nslookup app-server.corp.local` successfully returns the IPv4 address . Which of the following is the most likely cause of this issue?
- The DNS server has a configured IPv4 (A) record for the target host but lacks a corresponding IPv6 (AAAA) record.Answer
- BThe target server requires a Canonical Name (CNAME) record to automatically translate IPv4 A records into IPv6 host addresses.
- CThe `nslookup` tool automatically defaults to reading the local HOSTS file instead of contacting the network DNS server when querying AAAA records.
- DThe command-line lookup failed because IPv6 name resolution queries use TCP port 443 rather than standard DNS port 53.
Answer
The DNS server has a configured IPv4 (A) record for the target host but lacks a corresponding IPv6 (AAAA) record.
The standard `nslookup` command requests IPv4 address (A) records by default, which resolved successfully to . Specifying `-type=AAAA` forces the utility to explicitly query for an IPv6 host record. The non-existent domain error returned by the server confirms that while the host exists with an IPv4 A record, no corresponding IPv6 AAAA record has been added to DNS.
Step-by-Step Solution
Key Concept
DNS Command-Line Utilities and Resource Record Query Analysis