A server administrator deploys a new web server, web-srv01.corp.local, with the IP address 10.10.20.5. Users on the 10.10.30.0/24 subnet report they cannot access the web application using the server's FQDN. The administrator confirms they can successfully ping the server's IP address from a user's workstation but receive a "host unknown" error when pinging the FQDN. Which of the following is the MOST likely cause of this issue?
A network firewall is blocking HTTP traffic between the subnets.
The DNS server is missing the host (A) record for web-srv01.corp.local.
A user workstation's hosts file contains an incorrect entry for the server.
The default gateway on web-srv01.corp.local is misconfigured.
The correct answer is that the DNS server is missing the host (A) record. The scenario indicates that the server is reachable by its IP address from another subnet, but not by its Fully Qualified Domain Name (FQDN). This specific set of symptoms points directly to a name resolution problem. In a corporate network, DNS is the primary method for resolving hostnames to IP addresses. A missing or incorrect 'A' record for web-srv01.corp.local on the DNS server would prevent clients from being able to translate the name into the correct IP address, resulting in the "host unknown" error. Tools like nslookup could be used to directly query the DNS server and confirm the absence of the record.
A misconfigured default gateway on the server would prevent it from communicating with devices outside of its own subnet. Since users on a different subnet can successfully ping the server's IP address, routing is working correctly, and the gateway is not the issue.
A network firewall blocking port 80 (HTTP) or 443 (HTTPS) would prevent access to the web application, but it would block traffic sent to the IP address just as it would for the FQDN. Since a ping to the IP address is successful, the fundamental connectivity is present and the issue is name resolution, not a port block.
An incorrect entry in a single user's hosts file could cause the issue for that specific user, but it is not the most likely cause when multiple users are affected, as implied by the scenario. The central DNS server is the common element affecting all users.