What Is a Secondary DNS Server?
Every Internet user depends on the domain name system, and its servers, for their online presence. Secondary domain name system servers store copies of the DNS resource records from the primary server for better load balancing and redundancy. In this article, you’ll find out what a secondary DNS server is, how it works, and how it differs from a primary server.
What is a secondary DNS server?
A secondary DNS server is a backup server that stores copies of the DNS records from a primary DNS server. The information contained in this copy includes IP addresses, mail exchanger (MX) records, and other data vital for Internet traffic.
If the primary DNS server is unresponsive for any reason, the secondary DNS server can step in to support domain name resolution.
The secondary domain name system server gets its data through a process called zone transfer. This involves copying the DNS records from the primary DNS server or another secondary DNS server.
Since the secondary server's copy is read-only, any changes to the DNS records must be made on the primary server. These updates are then transferred to the secondary server to keep it current.
Through zone transfer, both servers will have identical DNS records and, in turn, maintain consistency across the network.
One of the main advantages of using a secondary DNS server is that it provides redundancy. While each DNS zone can only have one primary server, it can have multiple secondary servers. This setup prevents service disruptions, which could otherwise lead to significant problems for any organization focused on online activities.
Having secondary servers in the DNS hierarchy helps distribute the workload.
Why do you need a secondary DNS server?
A secondary DNS server matters to anyone who values the continuous availability of their online services. Relying solely on a primary DNS server creates a single point of failure, and this can be risky.
The entire network's functionality is at stake if a primary DNS server fails due to hardware issues, software glitches, or malicious attacks.
A backup is needed in such a scenario. A secondary DNS server mitigates this risk by taking over when the primary DNS server goes down.
As a user, you can still access websites, online services, and other resources without interruption. For businesses, this translates to less downtime, improved performance, and enhanced security.
How does a secondary DNS server work?
A secondary DNS server is a replica of a primary DNS server. It functions by periodically copying the DNS records from the latter to maintain an up-to-date version of the DNS records.
When a DNS request is sent, it first goes to the primary DNS server. If the primary server is available, it responds with the requested DNS record. If unreachable, the query is redirected to the backup server. This seamless handover ensures the user experience remains uninterrupted, even when a server runs into issues.
The secondary server is set up to handle DNS queries when the primary server cannot. It stays synchronized with the primary server, updating its DNS records whenever changes occur.
This is made possible through a process called zone transfer, which allows the backup server to receive updates from the primary server. The secondary DNS is ready to respond to any incoming queries with the current information.
In some cases, the secondary DNS server may also handle some DNS traffic to reduce the load on the primary server. This traffic distribution helps improve overall system reliability.
Benefits of using a secondary DNS server
Less downtime
The server adds resilience to the system, significantly reducing the chances of unwanted outages. It lets the system remain operational during downtimes. Users continue to access your online services without noticing any disruption as the secondary domain name system seamlessly replaces the primary server.
Improved performance
Distributing DNS traffic across multiple servers boosts the performance of the entire system. Looking at the effects, sharing the load means the DNS system can handle more queries simultaneously.
This, along with faster response times, is particularly beneficial for clients because it gives users a smoother browsing experience.
Backup plan
It serves as a vital backup when the primary server encounters issues. This redundancy adds an extra layer of security to your DNS infrastructure. While it safeguards against data corruption, the secondary DNS server can have the necessary DNS information in an emergency.
Load balancing
DNS load balancing distributes DNS queries across multiple name servers using a round-robin algorithm. This algorithm ensures that a different server handles each query to prevent any single server from becoming overloaded. As user traffic grows, additional servers can be added to manage the increased load.
Geographical redundancy
Placing secondary domain name system servers in different geographical locations avoids a single point of failure. The technique enhances the resilience of your DNS infrastructure.
If a localized outage affects one region, the secondary DNS servers in other locations can continue to operate without interruption. The deployment is valuable for global businesses that prioritize high availability across different areas.
Who uses secondary DNS servers?
Secondary DNS servers are for companies that operate online businesses. Organizations that manage critical operations are the beneficiaries at most. The servers guarantee that purchases and work continue without any hassle.
- Businesses and organizations are dependent on secondary DNS servers for various online operations. Customers build trust when they can consistently access the online service they seek.
- E-commerce platforms need high availability to process transactions effectively. The idea is that these platforms remain operational despite potential outages, so customers can complete transactions without experiencing any downtime.
- Internet service providers (ISPs) use secondary DNS servers to minimize disruptions to their subscribers' Internet service. A reliable DNS resolution signifies a stable Internet connection for users.
- Critical infrastructure providers, such as utilities, healthcare facilities, and financial institutions, count on secondary DNS servers for better service delivery. Latency can have serious consequences in these industries.
- Government agencies use a backup server to continuously provide websites, portals, and other online resources to citizens.
Whether you're a small business exchanging data or a large entity responsible for facilitating others, the benefits of secondary DNS servers provide a way to secure and protect online businesses and transactions.
What is the difference between primary and secondary DNS servers?
The main difference between primary and secondary servers lies in their roles. The primary DNS server holds the authoritative DNS records.
In contrast, the secondary DNS server receives copies of these records from the primary server through zone transfers. The secondary server's role is to provide redundancy and handle DNS queries when the primary server malfunctions.
| Primary DNS server | Secondary DNS server | |
| Role | Translates human-readable domain into IP address | Provides a backup for a primary server, receives and stores copies of DNS records |
| Authority | Sole authority over DNS records | No authority to modify DNS records |
| Data source | Original source of DNS records | Copies DNS records from the primary server |
| Updates | Directly managed and updated by administrators | Updates through zone transfers from the primary |
| Redundancy | Typically a single server, creating a single point of failure | Provides redundancy and backup for the primary server |
| Load distribution | Handles all DNS queries by default | Shares DNS query load with the primary server |
| Information | Contains data about the domain requested and the IP address as well | Contains data about a primary DNS server zone |
How to configure a secondary DNS server
If you're familiar with the domain name system and your computer's software, configuring a secondary server isn't difficult. Follow these steps to successfully install, set up, and test your server.
- Install the DNS server software. Install DNS server software on the secondary server. The software should be compatible with your existing network infrastructure and support the features you require.
- Edit configuration file. Edit the DNS configuration file on the secondary server. Define the zone for your domain, but this time, mark the zone as ‘slave’ or ‘secondary.’ This designation tells the server that it will act as a secondary domain name system server to receive the current info.
- Specify the primary server. In the zone definition, specify the IP address of the primary DNS server. The secondary server will use this address to perform zone transfers and keep its records up to date.
- Set up access control. If necessary, configure access control settings on the secondary DNS server. These settings restrict who can request zone transfers. Proper access control is crucial for maintaining the integrity of your DNS infrastructure.
- Start DNS service. After configuring the necessary settings, start the DNS service on the secondary server. This action initiates the server's role in responding to DNS queries and performing zone transfers from the primary server.
- Initiate zone transfer. The secondary DNS server will communicate with the primary server to initiate a zone transfer.
- Test configuration. Finally, test the configuration to verify that the secondary server can successfully serve DNS requests for your domain. Ensure that the secondary DNS server responds to queries as expected.
Choosing the right secondary DNS server provider
When evaluating providers, consider factors such as their network coverage, redundancy options, and support services. A good provider should offer global coverage, allowing you to place secondary domain name system servers in multiple regions for geographic redundancy.
You’ve seen how fundamental servers are in the DNS system. Look for a provider with robust security features like DDoS protection and access control. These features are essential for protecting your DNS servers from attacks.
Needless to say, a vendor with a strong track record is reliable. They offer customer support around the clock in case of any issues.
Secondary DNS server security
One of the leading security concerns for DNS servers is their vulnerability to DDoS attacks. In these attacks, malicious actors flood the server with an overwhelming amount of traffic, causing it to become unresponsive.
If a secondary domain name system server is attacked, your online service will go offline. The best recommendation is to deploy servers that operate within a DNS anycast network.
Anycast in a network addressing allows multiple servers in different geographical regions to share the same IP address. In case of an attack on one server, the traffic can be rerouted to other servers within the network.
Frequently asked questions
How does a secondary DNS server update its records?
It performs regular zone transfers from the primary DNS server to keep its records updated.
Is a secondary DNS server necessary for all domains?
While not mandatory, it's highly recommended for services that require high availability and reliability. If you don't want to manage the servers yourself, secondary DNS hosting is an option as a service that provides secondary servers for data security and management.
Can a secondary DNS Server exist without a primary DNS server?
No, a secondary domain name system server requires a primary DNS server to obtain and update DNS records through zone transfers.
