SK0-004 · Question #718
A server technician is notified that a server IP address is changing on the network. The technician changes the static IP address on the NIC to match the new address. However, when the technician…
The correct answer is B. DNS A record type C. DNS PTR record type. After a server IP change, both the DNS A record (forward lookup) and DNS PTR record (reverse lookup) must be updated because each independently caches the old address mapping.
Question
A server technician is notified that a server IP address is changing on the network. The technician changes the static IP address on the NIC to match the new address. However, when the technician issues the command with the hostname of the machine, the old IP address assignment is still being nslookup reported. The technician also performs a reverse DNS lookup using the old IP and verifies the FQDN of the server is reported. Given this scenario, which of the following should the technician inspect to resolve this issue? (Select TWO).
Options
- ADNS CNAME record type
- BDNS A record type
- CDNS PTR record type
- DDNS SRV record type
- EDNS MX record type
How the community answered
(39 responses)- A10% (4)
- B82% (32)
- D3% (1)
- E5% (2)
Why each option
After a server IP change, both the DNS A record (forward lookup) and DNS PTR record (reverse lookup) must be updated because each independently caches the old address mapping.
A DNS CNAME record maps an alias name to a canonical hostname, not to an IP address directly, so it has no effect on the IP returned by a forward lookup or the FQDN returned by a reverse lookup.
The DNS A record maps a hostname (FQDN) to an IPv4 address, and since nslookup using the hostname still returns the old IP, the A record in DNS has not been updated to reflect the new static address configured on the NIC.
The DNS PTR record enables reverse DNS lookup by mapping an IP address back to a hostname, and since querying the old IP still returns the server FQDN, the PTR record associated with the old IP must be deleted and a new PTR record created for the new IP.
A DNS SRV record specifies the host and port for specific network services and plays no role in hostname-to-IP or reverse IP-to-hostname resolution.
A DNS MX record identifies mail exchange servers for a domain and is entirely unrelated to resolving host addresses or reverse DNS lookups.
Concept tested: DNS A and PTR record updates after static IP address change
Source: https://learn.microsoft.com/en-us/windows-server/networking/dns/dns-top
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