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A user reports that the corporate web server cannot be accessed. A technician verifies that the web server can be accessed by its IP address. What are two possible causes of the problem? (Choose two.)

A user reports that the corporate web server cannot be accessed. A technician verifies that the web server can be accessed by its IP address. What are two possible causes of the problem? (Choose two.)

  • The web server is misconfigured.
  • The DNS server address is misconfigured on the workstation.
  • The network connection is down.
  • The default gateway address is misconfigured on the workstation.
  • The web server information is misconfigured on the DNS server.

The correct answers are:

  1. The DNS server address is misconfigured on the workstation.
  2. The web server information is misconfigured on the DNS server.

Understanding the Problem

When a user reports that a corporate web server cannot be accessed by its domain name, but the server is accessible via its IP address, it indicates an issue with the Domain Name System (DNS) configuration rather than a problem with the web server or network connectivity itself. Let’s explore the implications of these possible causes in detail.

The Role of DNS

DNS is a hierarchical and decentralized naming system that translates human-readable domain names (like www.example.com) into IP addresses (like 192.168.1.1), allowing users to access resources on the internet or intranet without needing to remember numerical addresses.

How DNS Works

  1. User Request: When a user types a domain name into a web browser, the browser sends a DNS query to resolve the domain name into an IP address.
  2. DNS Server Lookup: The local DNS resolver on the user’s workstation first checks its cache for a recently resolved address. If not found, it queries configured DNS servers.
  3. Response: The DNS server responds with the corresponding IP address, allowing the user’s browser to establish a connection to the web server.

Possible Causes of the Problem

  1. DNS Server Address is Misconfigured on the Workstation:
    • If the DNS server address configured on the workstation is incorrect, the workstation cannot reach the DNS server to resolve the domain name.
    • This misconfiguration may result from:
      • Manual entry errors in network settings.
      • DHCP issues where the workstation did not receive the correct DNS server settings.
    • Symptoms:
      • Users may receive “DNS server not responding” errors.
      • They may experience issues accessing websites by domain name while still being able to connect using IP addresses.
    • Resolution:
      • Verify the DNS settings on the workstation. This can typically be done by checking the network settings under the TCP/IP configuration. Ensure that the DNS server addresses are set to valid, operational DNS servers.
  2. Web Server Information is Misconfigured on the DNS Server:
    • If the DNS server has incorrect records for the web server, such as an outdated or incorrect IP address, it will not resolve the domain name to the correct address.
    • This misconfiguration can happen due to:
      • Recent changes to the server’s IP address that were not updated in the DNS records.
      • Typographical errors when entering records into the DNS management interface.
    • Symptoms:
      • The user may experience a “server not found” error or similar messages indicating that the domain name could not be resolved.
    • Resolution:
      • Check the DNS records for the web server on the DNS server. Ensure that the A record (or other relevant records) for the domain name points to the correct IP address of the web server.

Why Other Options Are Less Likely Causes

  1. The Web Server is Misconfigured:
    • Since the web server can be accessed by its IP address, it suggests that the web server itself is operational and correctly configured to respond to HTTP requests. A misconfiguration of the web server would typically manifest in issues when accessing it via the IP address, not just the domain name.
  2. The Network Connection is Down:
    • If the network connection were down, neither the IP address nor the domain name would resolve. Since the server is accessible via its IP address, this indicates that the network connection is functioning properly, at least for that specific server.
  3. The Default Gateway Address is Misconfigured on the Workstation:
    • A misconfigured default gateway would lead to issues in accessing external networks. However, since the web server is accessible via its IP address, this implies that the workstation can route to the server. If the gateway were misconfigured, users would generally face broader connectivity issues, affecting all devices outside their local subnet.

Detailed Troubleshooting Steps

To diagnose and resolve the issue effectively, follow these troubleshooting steps:

  1. Verify the Web Server’s DNS Records:
    • Use tools like nslookup or dig from a command prompt to check the DNS records for the web server’s domain name.
    • Example command: 
      nslookup www.example.com
    • Compare the returned IP address with the server’s actual IP address. If there’s a mismatch, update the DNS records.
  2. Check Workstation DNS Settings:
    • On Windows, open the Network and Sharing Center, click on “Change adapter settings,” then right-click on the active network connection and select “Properties.” Check the properties of Internet Protocol Version 4 (TCP/IPv4) for the DNS server addresses.
    • On Linux or macOS, check the /etc/resolv.conf file to confirm the DNS servers listed.
  3. Test DNS Resolution:
    • From the affected workstation, run a command prompt and use: 
      ping www.example.com
    • If this fails, but pinging the IP address succeeds, it confirms that the DNS is at fault.
  4. Check Local DNS Cache:
    • Sometimes, DNS resolution issues can be caused by cached entries. Flush the DNS cache using the command: 
      ipconfig /flushdns
    • Then try to access the domain again.
  5. Review DHCP Configuration:
    • If the workstation receives its IP address and DNS settings via DHCP, ensure that the DHCP server is configured correctly. Check for any scope options that specify the DNS server addresses.
  6. Network Tools for Troubleshooting:
    • Use network diagnostic tools such as traceroute or pathping to identify where the breakdown occurs when trying to access the server by domain name.
    • For instance: 
      traceroute www.example.com
    • This can help pinpoint network issues between the workstation and DNS servers.

Conclusion

In conclusion, if a user cannot access the corporate web server by its domain name but can connect via its IP address, it strongly indicates issues related to DNS configuration. The most likely causes are that either the DNS server address is misconfigured on the workstation, preventing it from resolving domain names, or that the DNS server itself has misconfigured records for the web server. Understanding the DNS infrastructure, conducting thorough troubleshooting, and making necessary adjustments can restore normal functionality, allowing users to access the web server using its domain name as intended.