What might be the problem if websites are accessible via IP but not URL?

• A. DNS blocking on UDP Port 53
• B. HTTP port 80 blocked
• C. TLS port 443 blocked
• D. NAT misconfiguration

Answer: (A)

When you can reach a site by its numeric address but not by its domain name, the issue is with name resolution rather than the web service itself. Browsers rely on DNS to translate a domain (like example.com) into an IP address before they can send a request. If DNS lookups fail, the domain name can’t be resolved, so the URL won’t load, even though knowing the IP would let you connect directly.

DNS queries typically use UDP on port 53, so blocking UDP port 53 prevents the client from asking DNS servers for translations. Without that resolution, typing the URL yields nothing, but using the IP address sidesteps DNS and can still reach the server, which is why this symptom points to DNS blocking on UDP port 53.

Blocking HTTP (port 80) or TLS (port 443) would generally disrupt traffic on the corresponding protocols, and NAT misconfiguration would usually affect routing more broadly. The DNS blockage explanation best matches the scenario.