N10-009 Question 64
Single answerHTTP: 80A help desk team reports that users on the internal network can successfully browse secure websites, but they cannot access a company intranet site by entering http://intranet.company.local in their browsers. A network technician confirms DNS is resolving the correct internal IP address and users can ping the web server. The web server is running, and HTTPS has not been configured for this site. Which issue is the MOST likely cause of the problem?
- A
TCP port 80 is blocked between the clients and the web server
- B
UDP port 80 is blocked between the clients and the web server
- C
TCP port 443 is blocked between the clients and the web server
- D
The server is missing an SSH service on TCP port 22
Show answer and explanation
Correct answer: A
Explanation
This question tests practical troubleshooting of application access using common port knowledge. HTTP uses TCP port 80, while HTTPS uses TCP port 443. Since DNS resolution is functioning and ping succeeds, the problem is unlikely to be name resolution or general Layer 3 connectivity. The failure affects an HTTP-only intranet site, so the technician should investigate filtering of TCP port 80 on the server firewall, client path, or an intervening ACL/firewall. This aligns with standard networking references and vendor documentation such as IANA service name/port number assignments and common web server configuration practices, where HTTP is associated with TCP 80.
- A. Correct.
Correct. Standard HTTP traffic uses TCP port 80. In this scenario, DNS resolution works and ICMP ping succeeds, so basic name resolution and IP connectivity are present. Because the site is accessed with http:// and HTTPS is not configured, the most likely issue is that TCP port 80 is being filtered by a host firewall, network firewall, or ACL between the clients and the server.
- B. Incorrect.
Incorrect. HTTP does not use UDP port 80 for normal web browsing. A candidate might choose this if they remember the port number but confuse the transport protocol. Standard HTTP communication is connection-oriented and runs over TCP, not UDP.
- C. Incorrect.
Incorrect. TCP port 443 is used for HTTPS, not HTTP. The scenario specifically states that HTTPS has not been configured and users are trying to reach the site with http://, so blocking 443 would not explain why this HTTP-only intranet site is unavailable.
- D. Incorrect.
Incorrect. SSH on TCP port 22 is used for secure remote administration, not for delivering web pages to browser clients. Someone might choose this if they are thinking generally about server access, but the issue described is specifically about browser access to an HTTP site.