In this IT Pro Challenge lab, learners will become familiar with configuring both Azure and non-Azure provided DNS server settings in the Azure portal. Learners will also use the PuTTY tool locally to view the contents of the Linux DNS configuration files. As proof of concept, you will use the nslookup and ping commands to verify the DNS server settings. Configuring DNS is an important part of understanding concepts related to websites and network protocols. The skills acquired in this lab are useful for a career as a network or system administrator.
The scenario for this virtual lab is that you are a system administrator, and your company uses Ubuntu Linux virtual machines in Microsoft Azure. Your job is to ensure that the Domain Name Server (DNS) name resolution is configured for Linux. To accomplish your goal, you will first verify that Azure-provided DNS name resolution is functioning properly. Then you will configure Azure DNS settings to point to external DNS servers for name resolution.
You will use the free PuTTY tool from your local computer to remotely manage the Linux virtual machine over a Secure Shell (SSH) connection. If you don’t already have it installed, you need to download and install the PuTTY tool on your computer using the default installation options. PuTTY is a free network file transfer application that supports rlogin (remote login) as well as several network protocols (Example: SCP, SSH, and Telnet).
Test Azure-provided DNS settings
To begin the lab, you need to sign into the Azure portal. From the All Resources view, navigate to the provided virtual network (Vnet) and view the DNS servers. You will notice that the default is Azure-provided, which means that all Azure virtual machines in the Vnet use the DNS server settings.
NOTE: You can configure DNS server settings for an individual network interface, and that would take precedence over the Vnet settings.
Now you will use the PuTTY tool on your local PC to connect to the Linux1 public IP address and then use the cat /etc/resolv.conf command to view the contents of the Linux DNS configuration file. Note the Azure DNS Server IP address; you will need it later in the lab for comparison purposes.
As proof of concept, you will use the ping [url] command to verify that the [url] is being resolved to an IP address. Use the nslookup command, enter the [url], and verify that the Azure DNS server is resolving the [url] to the IP address.
Configure an Azure VNet with a custom DNS server
Finally, you will use the Azure portal to configure a custom DNS server (rather than the Azure-provided default) of 126.96.36.199 for the provided VNet (MyVNET).
NOTE: When working in the Microsoft cloud environment, It is always good practice to use the Azure portal to configure DNS server name resolution settings, as opposed to on the operating system itself.
You must restart the virtual machine before your custom DNS server settings can be applied and picked up by the VNet. You will now return to the open PuTTY window and connect to the Linux1 public IP address and then use the cat /etc/resolv.conf command to view the contents of the Linux DNS configuration file. Now you should see that the nameserver IP address is the custom DNS server you just created (188.8.131.52).
As proof of concept that you are using the new, non-Azure DNS server, use the ping __[url] command to verify that the provided [url] is being resolved to an IP address. Use the __nslookup command, enter the [url], and verify that the custom (non-Azure) DNS server is resolving the [url] to an IP address. The IP address you see here should be the same as in the previous step, but the server address is now 184.108.40.206.
By taking this virtual lab, you will learn how to use the Azure portal to configure the default Azure-provided DNS server and a custom, non-Azure DNS server for a VNet. You will ensure that DNS name resolution works properly, and you will use the PuTTY tool to test that both DNS server settings are working properly.