Learn how to setup caching only DNS server on CentOS 7 to improve DNS resolution speed and reduce network traffic. This step-by-step guide covers installation, configuration, and best practices. #centlinux #linux #dns
DNS stands for Domain Name System. It is a crucial component of the internet’s infrastructure that translates human-friendly domain names into IP addresses, which computers use to identify and communicate with each other over the internet. DNS acts like a phonebook for the internet, allowing users to access websites using easy-to-remember domain names instead of numeric IP addresses.
Here’s a detailed breakdown of what DNS is, how it works, and why it’s important.
www.example.com
) into IP addresses (like 192.0.2.1
).The DNS process involves several key components and steps to resolve a domain name into an IP address:
.com
, .org
).example.com
).www.example.com
, com
is the top-level domain, example
is the second-level domain, and www
is a subdomain.Here’s a simplified view of the DNS hierarchy:
plaintextCopy code+------------------+
| Root Level |
| (.) |
+------------------+
|
v
+------------------+
| TLD Level |
| (.com, .org, etc.) |
+------------------+
|
v
+------------------+
| Second-Level |
| Domain Level |
| (example.com) |
+------------------+
|
v
+------------------+
| Subdomain Level |
| (www.example.com) |
+------------------+
Read Also: How to setup DNS Authoritative Server in CentOS 7
A Caching Only DNS Server is a specialized type of DNS server that performs domain name resolution by querying other DNS servers and storing (caching) the results for future use. Unlike authoritative DNS servers, which provide DNS records for a specific domain, caching-only DNS servers are primarily focused on resolving domain names by leveraging cached data to improve efficiency and reduce network traffic.
Here’s a detailed breakdown of what a caching-only DNS server is, how it works, and its benefits.
Here’s a step-by-step explanation of how a caching-only DNS server processes DNS queries:
www.example.com
).Component | Description |
---|---|
DNS Cache | Stores DNS query results to speed up future requests. |
Forwarding | Forwards DNS queries to upstream DNS servers if the cache does not contain the required record. |
TTL (Time-To-Live) | Specifies how long a DNS record is stored in the cache. |
DNS Resolver | The component that resolves domain names to IP addresses. |
Benefit | Description |
---|---|
Improved Performance | Reduces latency and speeds up domain resolution by using cached records. |
Reduced Network Traffic | Lowers the number of queries sent to external DNS servers, saving bandwidth. |
Decreased DNS Resolution Times | Faster response times for repeated DNS queries due to cached data. |
Enhanced Reliability | Provides a fallback for DNS queries if upstream DNS servers are unavailable. |
Cost Efficiency | Reduces reliance on external DNS services, potentially lowering costs. |
Use Case | Description |
---|---|
Internal DNS Resolver | Used in organizations to handle DNS requests for internal networks. |
Home Network DNS Server | Provides DNS resolution for home networks, improving speed and reliability. |
ISP DNS Server | ISPs use caching-only servers to manage DNS requests for multiple customers. |
DNS Query Testing | For testing DNS configurations and analyzing DNS performance. |
Recommended Online Training: Learn Bash Shell in Linux for Beginners
BIND (Berkeley Internet Name Domain) is a famous DNS server in RHEL 7 and previous releases. BIND was used to configure Authoritative DNS servers as well caching-only DNS servers. However, In RHEL 7 we also have unbound to easily configure a Caching-only DNS Server. We recommend the use of unbound DNS Server, because it is simple and convenient.
Connect to the dns-01.example.com with ssh and check current DNS Settings of the Server.
# cat /etc/resolv.conf # Generated by NetworkManager domain localdomain search localdomain example.com nameserver 192.168.116.2
Above command shows us the DNS server in use. Install unbound to configure a Caching-only DNS server.
# yum install -y unbound
Configure unbound DNS server settings.
# vi /etc/unbound/unbound.conf
Find and adjust following settings in the above file.
interface: 0.0.0.0
access-control: 0.0.0.0/0 allow
domain-insecure: "example.com"
forward-zone:
name: "."
forward-addr: 192.168.116.2
Check unbound Configurations for possible syntax errors.
# unbound-checkconf unbound-checkconf: no errors in /etc/unbound/unbound.conf
Start and enable unbound service.
# systemctl start unbound ; systemctl enable unbound
Allow DNS service in Linux firewall.
# firewall-cmd --permanent --add-service=dns ; firewall-cmd --reload success success
Set newly configured DNS Server as the primary DNS server for the machine.
# nmcli connection modify eno16777728 ipv4.dns 192.168.116.11 # nmcli connection down eno16777728 ; nmcli connection up eno16777728 Connection successfully activated (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/4) # cat /etc/resolv.conf # Generated by NetworkManager domain localdomain search localdomain example.com nameserver 192.168.116.11
Check DNS Server by pinging an Internet Server by hostname.
# ping www.yahoo.com PING atsv2-fp.wg1.b.yahoo.com (98.137.246.8) 56(84) bytes of data. 64 bytes from media-router-fp2.prod1.media.vip.gq1.yahoo.com (98.137.246.8): icmp_seq=2 ttl=128 time=275 ms 64 bytes from media-router-fp2.prod1.media.vip.gq1.yahoo.com (98.137.246.8): icmp_seq=3 ttl=128 time=271 ms
Our Caching only DNS Server in RHEL 7 has been configured successfully.
If you are new to Linux and facing difficulty in working at Linux Bash prompt. We recommend that, you should read The Linux Command Line, 2nd Edition: A Complete Introduction by William Shotts.
Setting up a caching-only DNS server on CentOS 7 is a powerful way to enhance your network’s efficiency and performance. By configuring a caching-only DNS server, you can significantly reduce DNS resolution times, decrease the load on upstream DNS servers, and improve the overall reliability of your DNS queries. Whether you are looking to optimize your home network, manage internal DNS requests for a business, or implement a solution for a service provider, this setup offers a robust and scalable solution for DNS resolution challenges.
Ready to improve your DNS infrastructure? If you need professional assistance with setting up or configuring a caching-only DNS server on CentOS 7, I’m here to help! Check out my Fiverr profile for expert services tailored to your DNS needs.
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It's awesome work.