DNS Name Resolution 1. INTRODUCTION. 2. Steps in the Lab. 3. Configuring the Network

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1 DNS Name Resolution 1. INTRODUCTION If I type on a web browser I will get the Google homepage. This is the IP address of this web site (server that gives me this website). This is how computers connect in a network via IP addresses. I can simply use the IP address for all my web browsing. If I need to go to facebook I can type ( ), but these are really difficult to remember ( ) and therefore we use the Domain Name Service (DNS). We are using DNS every time we visit a website. Any URL that we type in the browser will be converted to an IP address. This is the address of the server from which you have requested the page. We are just not aware of it, as it happens in the background. 2. Steps in the Lab Domain Name server resolves the server IP address ( ) from the server name ( So here the first step is to install a DNS server that would convert the Internet name to IP address. 3. Configuring the Network The Windows operating systems uses DNS to resolve the computers in a LAN network. Therefore the next step is to configure a Domain Name server for our computer lab. To start any server we need to assign it an IP address. This is what we are doing in the steps mentioned in Configuration of Network from 1 to Now click on Start. 2. Go to Administrative Tools - Server Manager. 3. In the Left Pane, click on Roles. 4. In the Right Side, click on Add Roles. 5. Click on Next in the New Window that opens. 6. Check DNS Server. 7. Click on "Install DNS Server anyway (not recommended)". 8. Click on Next. 9. Click on Next again. 10. Now click Install. 11. After the Installation completes, click on Close. 12. You have now completed the Installation of DNS Server. Close the Server Manager now. And we assign an IP address to the DNS server. 1. Click on Start. 2. Go to Control Panel. 3. Find and double click "Network and Sharing Center".

2 4. Find and click on the link of "View Status" under Public Network on the right of Local Area Connection. 5. Click on Properties in the new window that pops up. 6. Double Click on "Internet Protocol Version 4 (TCP/IPv4)". 7. Click on "Use the following IP Address" and fill in the following values in the respective boxes. IP Subnet Mask: (Filled in Automatically) Default Gateway: Under DNS Server Addresses, give the Preferred DNS Server address as Leave the Alternate DNS Server Address field blank. 10. Click on OK. 11. Click on OK again on the Local Area Connection Properties dialog box. 12. Click on Close on the Local Area Connection Status dialog box. 13. Close the Network and Sharing Center. 4. Configuring DNS Server 4.1 Forward Lookup Zones vs. Reverse Lookup Zones In the next couple of steps you are configuring the forward and the reverse lookup zones. A forward look up zone is nothing more than converting an address from to its corresponding IP address. A reverse look up zone is simply the reverse: converting the IP address to the Internet name. The Internet name can be divided into many levels. In the example of you have the top level domain and the second level domains. 4.2 Top Level Domain and Second Level Domains The.com part of the address is called Top Level Domains or abbreviated as TLD. TLD can be.com,.coop,.edu, etc. Second level domains contains businesses that registers their domain with the top level domain, for example technowidget that registers with.com In this lab exercise, the first couple of steps walk you through adding forward and reverse lookup zones, which takes care of the Internet name to IP address conversion and vice versa. We can further have a division called the sub domain. As given in the example below, a subdomain can be called research or johnserver and a host computer of this subdomain can be called or in case of research it can be

3 In the next couple of steps we are adding the subdomain such as research, johnserver and mail. A company that registers for a domain can divide it into subdomains like tamu.edu, a subdomain can be .tamu.edu or howdy.tamu.edu which are subdomains of the main domain tamu.edu. 4.3 Primary and Secondary Servers What we are configuring in this lab exercise is the primary server, which contains all the information for the hosts in the domain and updates for the secondary server. We make the forward lookup and the reverse look up zones in the primary server. A secondary server is mainly used for load balancing. When the secondary server first starts, it gets all the data from the primary server and it periodically asks the primary server for updates. The updates in the address are recorded by the primary server by updating the serial number. As the serial number changes, the secondary server is updated by the primary server. This is done towards the end of the lab exercise. 1. Configuring DNS Server 1. Click Start. 2. Go to Administrative Tools DNS. 3. Click on the "+" Sign under the DNS Heading in the new window that opens. 4. Left Click on Forward Lookup Zones. 5. Now Right Click on Forward Lookup Zones and click on New Zone. 6. Click Next on the New Window that pops up. 7. Click Next again (The default selection is Primary Zone). 8. Give the Zone Name as: technowidgets.com and click Next. 9. Click Next again (on the new file name technowidgets.com.dns ). 10. Click Next again (on Do not allow dynamic updates). 11. Click Finish. 12. Left Click Reverse Lookup Zones. 13. Now Right Click Reverse Lookup Zones. 14. Click on New Zone. 15. Click on Next in the new window that pops up. 16. Click on Next (The default selection is Primary Zone). 17. Click on Next again (Make sure that the default selection is IPv4 Reverse Lookup Zone). 18. On the new screen that comes, give the Network ID as and click on Next. 19. Click on Next on the new screen (Let the Default Selection be: Create a new file with the file name as: " in-addr.arpa.dns"). 20. Click on Next (Default Selection: Do Not Allow Dynamic Updates). 21. Click Finish. 22. Click on the "+" Sign on the left of "Forward Lookup Zones". 23. Right click on "technowidgets.com".

4 24. Click on New Host. 25. In the new window that pops up, in the Name Field, give the name as: YourNameServer. For Example: If your name is John, you give the name as : johnserver 26. In the IP Address field: Make Sure the "Created Associated Pointer (PTR) Record" checkbox is checked. 28. Click on Add Host. 29. Click on OK. 30. Now we need to create two more hosts, so we continue the process as follows: a. In the Name Field, give the name as: research. b. In the IP Address field: c. Make Sure the "Created Associated Pointer (PTR) Record" checkbox is checked. d. Click on Add Host. e. Click on OK. 31. Again, we continue to make the next host: a. In the Name Field, give the name as: mail. b. In the IP Address field: c. Make Sure the "Created Associated Pointer (PTR) Record" checkbox is checked. d. Click on Add Host e. Click on OK. f. Now Click on Done. 32. Again, right click on technowidgets.com under Forward Lookup Zones. 33. Click on New Alias (CNAME). 34. In the new window that pops up, in the Alias Name field, give the Alias as : www 35. In the last field, Fully Qualified Domain Name (FQDN), type: yournameserver.technowidgets.com. For Example: johnserver.technowidgets.com. 36. Click on OK. 37. Again, right click on technowidgets.com under Forward Lookup Zones. 38. Click on New Mail Exchanger (MX). 39. In the new window that pops up, leave the Host and Child Domain field blank. 40. In the Fully Qualified Domain Name (FQDN) field, type: mail.technowidgets.com. 41. Leave the Mail Server Priority to the default value of Click on OK. 43. Again, right click on technowidgets.com under Forward Lookup Zones. 44. Click on Properties. 45. Go to Start of Authority (SOA) tab. 46. Change the Serial Number to Change the primary server to yournameserver.technowidgets.com. 48. Change the responsible person to admn.technowidgets.com. 49. Leave the other values as they are. 50. Now go to Name Servers tab. 51. Select the default name in the list and click on Remove.

5 52. Click on Add and give the name as: yournameserver.technowidgets.com and click on Resolve. 53. If you have done everything as directed, the IP Address should be shown as Validated. 54. Click on OK. 55. Click on OK again. 56. Check if you have followed all the steps properly: 1. Using Ping to Test Connectivity: We need to check whether the DNS Server is able to resolve the host name into an IP Address. Start Command Prompt from the Start Menu and type the following and then hit Enter: ping If all the steps were performed as directed, it should generate an output somewhat like the following: Pinging yournameserver.technowidgets.com [ ] with 32 bytes of data: Reply from : bytes=32 time=3ms TTL=128 Reply from : bytes=32 time=1ms TTL=128 Reply from : bytes=32 time<1ms TTL=128 Reply from : bytes=32 time<1ms TTL=128 Ping statistics for Packets: Sent = 4, Received = 4, Lost = 0 (0% loss) Approximate Round-trip times in milli-seconds: Minimum = 0ms, Maximum = 3ms, Average = 0ms

6 2. Using nslookup to Check DNS: Another utility specifically designed to test DNS functionality is nslookup. The first two letters in the name of the utility s name stand for name server, indicating that nslookup is designed to look up information in a name (DNS) Server. The utility works in two modes: command-line mode and interactive mode. Command-line mode: a. Start Command Prompt from the Start Menu and type: nslookup You will get an output as follows: Server: yournameserver.technowidgets.com Name: yournameserver.technowidgets.com Aliases: Interactive-mode: Type nslookup in Command-Prompt and hit Enter. You will get an output as follows:

7 Default Server: yournameserver.technowidgets.com >_ Now type: research.technowidgets.com You will get an output as follows: Server: yournameserver.technowidgets.com Name: research.technowidgets.com Address: >_ Type exit to quit from the command prompt.