Merge pull request #234115 from divargas-msft/patch-3

[Doc-a-thon] Updating azure-dns.md

Author: American-Dipper

articles/virtual-machines/linux/azure-dns.md

@@ -5,7 +5,7 @@ author: RicksterCDN
 ms.service: virtual-machines
 ms.subservice: networking
 ms.topic: conceptual
-ms.date: 10/19/2016
+ms.date: 04/11/2023
 ms.author: rclaus
 ms.collection: linux
 
@@ -32,9 +32,11 @@ The following table illustrates scenarios and corresponding name resolution solu
 | Reverse DNS for internal IPs |[Name resolution using your own DNS server](#name-resolution-using-your-own-dns-server) |n/a |
 
 ## Name resolution that Azure provides
+
 Along with resolution of public DNS names, Azure provides internal name resolution for virtual machines and role instances that are in the same virtual network. In virtual networks that are based on Azure Resource Manager, the DNS suffix is consistent across the virtual network; the FQDN is not needed. DNS names can be assigned to both network interface cards (NICs) and virtual machines. Although the name resolution that Azure provides does not require any configuration, it is not the appropriate choice for all deployment scenarios, as seen on the preceding table.
 
 ### Features and considerations
+
 **Features:**
 
 * No configuration is required to use name resolution that Azure provides.
@@ -52,7 +54,8 @@ Along with resolution of public DNS names, Azure provides internal name resoluti
     Names must use only 0-9, a-z, and '-', and they cannot start or end with a '-'. See RFC 3696 Section 2.
 * DNS query traffic is throttled for each virtual machine. Throttling shouldn't impact most applications.  If request throttling is observed, ensure that client-side caching is enabled.  For more information, see [Getting the most from name resolution that Azure provides](#getting-the-most-from-name-resolution-that-azure-provides).
 
-### Getting the most from name resolution that Azure provides
+### Getting the most from name resolution that Azure provides\
+
 **Client-side caching:**
 
 Some DNS queries are not sent across the network. Client-side caching helps reduce latency and improve resilience to network inconsistencies by resolving recurring DNS queries from a local cache. DNS records contain a Time-To-Live (TTL), which enables the cache to store the record for as long as possible without impacting record freshness. As a result, client-side caching is suitable for most situations.
@@ -61,27 +64,89 @@ Some Linux distributions do not include caching by default. We recommend that yo
 
 Several different DNS caching packages, such as dnsmasq, are available. Here are the steps to install dnsmasq on the most common distributions:
 
-**Ubuntu (uses resolvconf)**
-  * Install the dnsmasq package (“sudo apt-get install dnsmasq”).
+# [Ubuntu](#tab/ubuntu)
+
+1. Install the dnsmasq package:
+
+```bash
+sudo apt-get install dnsmasq
+```
+
+2. Enable the dnsmasq service:
+
+```bash
+sudo systemctl enable dnsmasq.service
+```
+
+3. Start the dnsmasq service:
+
+```bash
+sudo systemctl start dnsmasq.service
+```
+
+# [SUSE](#tab/sles)
+
+1. Install the dnsmasq package:
+
+```bash
+sudo zypper install dnsmasq
+```
+
+2. Enable the dnsmasq service:
+
+```bash
+sudo systemctl enable dnsmasq.service
+```
+
+3. Start the dnsmasq service:
+
+```bash
+sudo systemctl start dnsmasq.service
+```
+
+4. Edit `/etc/sysconfig/network/config` file using a text editor, and change `NETCONFIG_DNS_FORWARDER=""` to `dnsmasq`.
+5. Update `/etc/resolv.conf` to set the cache as the local DNS resolver.
+
+```bash
+sudo netconfig update
+```
 
-**SUSE (uses netconf)**:
-1. Install the dnsmasq package (“sudo zypper install dnsmasq”).
-2. Enable the dnsmasq service (“systemctl enable dnsmasq.service”).
-3. Start the dnsmasq service (“systemctl start dnsmasq.service”).
-4. Edit “/etc/sysconfig/network/config”, and change NETCONFIG_DNS_FORWARDER="" to ”dnsmasq”.
-5. Update resolv.conf ("netconfig update") to set the cache as the local DNS resolver.
+# [CentOS/RHEL](#tab/rhel)
 
-**CentOS by Rogue Wave Software (formerly OpenLogic; uses NetworkManager)**
-1. Install the dnsmasq package (“sudo yum install dnsmasq”).
-2. Enable the dnsmasq service (“systemctl enable dnsmasq.service”).
-3. Start the dnsmasq service (“systemctl start dnsmasq.service”).
-4. Add “prepend domain-name-servers 127.0.0.1;” to “/etc/dhclient-eth0.conf”.
-5. Restart the network service (“service network restart”) to set the cache as the local DNS resolver
+1. Install the dnsmasq package:
+
+```bash
+sudo yum install dnsmasq -y
+```
+
+2. Enable the dnsmasq service:
+
+```bash
+sudo systemctl enable dnsmasq.service
+```
+
+3. Start the dnsmasq service:
+
+```bash
+sudo systemctl start dnsmasq.service
+```
+
+4. Add `prepend domain-name-servers 127.0.0.1;` to `/etc/dhcp/dhclient.conf`.
+
+```bash
+sudo echo "prepend domain-name-servers 127.0.0.1;" >>  /etc/dhcp/dhclient.conf
+```
+
+5. Restart the network service to set the cache as the local DNS resolver
+
+```bash
+sudo systemctl restart NetworkManager
+```
 
 > [!NOTE]
-> : The 'dnsmasq' package is only one of the many DNS caches that are available for Linux. Before you use it, check its suitability for your needs and that no other cache is installed.
->
->
+> The `dnsmasq` package is only one of the many DNS caches that are available for Linux. Before you use it, check its suitability for your needs and that no other cache is installed.
+
+---
 
 **Client-side retries**
 
@@ -92,25 +157,33 @@ DNS is primarily a UDP protocol. Because the UDP protocol doesn't guarantee mess
 
 To check the current settings on a Linux virtual machine, 'cat /etc/resolv.conf', and look at the 'options' line, for example:
 
+```bash
+sudo cat /etc/resolv.conf
+```
+
 ```config-conf
 options timeout:1 attempts:5
 ```
 
-The resolv.conf file is auto-generated and should not be edited. The specific steps that add the 'options' line vary by distribution:
+The `/etc/resolv.conf` file is auto-generated and should not be edited. The specific steps that add the 'options' line vary by distribution:
 
 **Ubuntu** (uses resolvconf)
-1. Add the options line to '/etc/resolvconf/resolv.conf.d/head'.
-2. Run 'resolvconf -u' to update.
+
+1. Add the options line to `/etc/resolvconf/resolv.conf.d/head` file.
+2. Run `sudo resolvconf -u` to update.
 
 **SUSE** (uses netconf)
-1. Add 'timeout:1 attempts:5' to the NETCONFIG_DNS_RESOLVER_OPTIONS="" parameter in '/etc/sysconfig/network/config'.
-2. Run 'netconfig update' to update.
+
+1. Add `timeout:1 attempts:5` to the `NETCONFIG_DNS_RESOLVER_OPTIONS=""` parameter in `/etc/sysconfig/network/config`.
+2. Run `sudo netconfig update` to update.
 
 **CentOS by Rogue Wave Software (formerly OpenLogic)** (uses NetworkManager)
-1. Add 'RES_OPTIONS="timeout:1 attempts:5"' to '/etc/sysconfig/network'.
-2. Run 'service network restart' to update.
+
+1. Add `RES_OPTIONS="timeout:1 attempts:5"` to `/etc/sysconfig/network`.
+2. Run `systemctl restart NetworkManager` to update.
 
 ## Name resolution using your own DNS server
+
 Your name resolution needs may go beyond the features that Azure provides. For example, you might require DNS resolution between virtual networks. To cover this scenario, you can use your own DNS servers.  
 
 DNS servers within a virtual network can forward DNS queries to recursive resolvers of Azure to resolve hostnames that are in the same virtual network. For example, a DNS server that runs in Azure can respond to DNS queries for its own DNS zone files and forward all other queries to Azure. This functionality enables virtual machines to see both your entries in your zone files and hostnames that Azure provides (via the forwarder). Access to the recursive resolvers of Azure is provided via the virtual IP 168.63.129.16.