> For the complete documentation index, see [llms.txt](https://riteshs4hu.gitbook.io/infosec-notes/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://riteshs4hu.gitbook.io/infosec-notes/linux-server-administrator/servers-configurations-centos7/domain-name-system-dns.md).

# Domain Name System (DNS)

## Cache Only DNS.

* **Check Hostname.**

```
hostname
```

* **Change Hostname And Domain Name.**

```
vim /etc/hostname #hostname.domain-name.top_level_domain_name
```

**Change DNS.**

```
vim /etc/sysconfig/network-scripts/ifcfg-enp0s3
```

```
Search DNS
Enter local IP

DNS1=127.0.0.1
```

* **Install Cache Tools.**

```
yum install bind*
```

* **Edit Configure File.**

```
vim /etc/named.conf
```

```
Listen-on port 53 { 127.0.0.1; Your-IP;};

allow-query {localhost; query-resolve-ip; };
```

* **Start Cache Service.**

```
systemctl enable named.service
```

```
systemctl restart named.service
```

* **Enable DNS Port in Firewall**

```
vim /etc/sysconfig/iptables
```

```
-A INPUT -p UDP --dport 53 -j ACCEPT
```

```
systemctl restart iptables
```

***

## Primary DNS/Master DNS

Primary DNS (Domain Name System) is a server that translates human-readable domain names into numerical IP addresses. When you type a website address into your browser, your computer sends a request to the primary DNS server associated with your internet service provider (ISP) to resolve the domain name into an IP address. The primary DNS server then sends a response with the IP address, which your computer uses to establish a connection to the website's server and load the website.

### Type of Primary DNS/Master DNS

* **Forwarder Zone**

  A Forward DNS lookup is used to convert a domain name to an IP address.
* **Reverse Zone**

  A reverse DNS lookup is used to convert an IP address to a domain name.

#### Forwarder Zone Configuration

**1. Edit File**

```
vim /etc/named.rfc1912.zones
```

**2. Make Zone**

![Zone](https://github.com/Mr-Secure-Code/Linux_Server/blob/main/Red%20HAT/DNS/Images/Zone.png?raw=true)

```
1. Zone Name.
2. Zone Type.
3. Zone New Filename (File Extension Match with zone name should be)
```

**3. Make A Zone File**

```
cp /var/named/named.localhost /var/named/zone_file_name
```

**4. Change file group**

```
chgrp named /var/named/zone_file_name
```

**5. Edit Zone File**

```
vim /var/named/zonefilename
```

![Zone File](https://github.com/Mr-Secure-Code/Linux_Server/blob/main/Red%20HAT/DNS/Images/ZoneFile.png?raw=true)

```
First, enter your name server.
Second name server.
Third, make a record.
```

**6.Start Service**

```
systemctl restart named
```

**7. Check Mistakes.**

```
named-checkconf
```

```
named-checkzone zonename /var/named/zone_file_name.
```

#### Reverse Zone Configuration.

**1. Make A Reverse Zone**

```
vim /etc/named.rfc1912.zones
```

![Reverse Zone](https://github.com/Mr-Secure-Code/Linux_Server/blob/main/Red%20HAT/DNS/Images/Revers%20Zone.png?raw=true)

```
1. Enter Network IP Reverse Order.
2. Enter Any Name File.
```

**2. Make Zone File**

```
cp /var/named/named.localhost /var/named/zone_file_name.
```

**3. Edit Zone File**

```
vim /var/named/zone_file_name
```

![Reverse Zone File](https://github.com/Mr-Secure-Code/Linux_Server/blob/main/Red%20HAT/DNS/Images/Revers%20Zone%20File.png?raw=true)

```
1. Enter Your Name Server.
2. Enter Your Name Server.
3. Your Name Server PTR Record.
4. Other Records.
```

**4. Change File Group.**

```
chgrp named zone_file_name.
```

**5. Start Service**

```
systemctl restart named
```

***

## Secondary/Slave DNS

**1. Make A Secondary Zone.**

![Slave Zone](https://github.com/Mr-Secure-Code/Linux_Server/blob/main/Red%20HAT/DNS/Images/Slave%20Zone.png?raw=true)

```
First, enter the master server name.
Second, enter zone type.
Third, enter the zone file name.
Fourth, enter the master DNS IP.
```

**2. Start Service.**

```
systemctl restart named
```

**3. Change Primary DNS Settings.**

![Master Changes](https://github.com/Mr-Secure-Code/Linux_Server/blob/main/Red%20HAT/DNS/Images/Master%20Changes.png?raw=true)

```
First, enter your primary name server.
Second, enter the primary name server.
Third, enter the slave name server.
Fourth, make A records.
```

**4. Restart Service.**

```
systemctl restart named
```

***

## Forwarders DNS Server

* **Edit File**

```
vim /etc/named.conf
```

* **Search recursion And insert This Line**.

```
forwarders { forwardersIP; };
```

* **Check Forwarders Query**

```
tcpdump -n -t udp port 53
```