Skip to main content

Authoritative DNS Servers Delegation and Internal DNS Explained

DNS (Domain Name System) plays a critical role in how users and systems find resources on the internet or within internal networks. Whether it's managing an internal domain in an enterprise or delegating parts of a domain for traffic distribution, DNS setups vary widely depending on needs. In this blog post, we’ll break down the different types of DNS setups, including authoritative DNS servers, DNS delegation, and how internal DNS functions within organizations.

1. Authoritative DNS Server

An Authoritative DNS server is the final source of truth for a specific domain. When someone queries a domain (e.g., example.com), the authoritative DNS server for that domain holds the DNS records (A records, CNAME, MX, etc.) and responds with the corresponding IP address.

Key Points:

  • Who can host it? Authoritative DNS servers are often hosted by domain registrars (e.g., GoDaddy, Namecheap) or cloud DNS providers (e.g., AWS Route 53, Cloudflare). However, organizations can also host their own authoritative DNS servers internally for greater control.
  • External DNS Resolution: Authoritative DNS servers are used to resolve public-facing domain names (e.g., www.example.com) for users all over the world.

Example:

If you purchase example.com from GoDaddy and use their DNS hosting service, GoDaddy’s authoritative DNS servers will store your DNS records and respond to DNS queries for that domain.

2. Internal DNS

An Internal DNS server is used within an enterprise network to resolve internal domain names. It is commonly found in Active Directory environments, where DNS is integrated with the network for resolving resources like workstations, servers, and internal applications.

Key Points:

  • Internal Name Resolution: Internal DNS servers typically manage private, non-public domains (e.g., company.local or internal.company.com) that are only used within the organization.
  • Not Publicly Exposed: Internal DNS servers are not exposed to the public internet. External queries for public domains like www.example.com are usually forwarded to external DNS resolvers.
  • Self-Hosted DNS: Many organizations prefer to manage their DNS infrastructure internally for better security and performance control.

Example:

Within a company, an internal DNS server might resolve the domain internal.company.com for local resources. Employees querying internal.company.com will get responses from the company’s internal DNS server, which is not accessible from the public internet.

3. DNS Delegation

DNS Delegation is the process of delegating responsibility for a subdomain to another DNS server. It’s commonly used when an organization wants a different system to manage DNS for a subdomain (e.g., delegating gslb.example.com to an F5 GTM for Global Server Load Balancing).

Key Points:

  • Delegating Subdomains: You can delegate authority for subdomains (e.g., sub.example.com) to another DNS server, while still retaining control of the main domain.
  • NS Records: Delegation is done by adding Name Server (NS) records in the authoritative DNS server for the main domain. These records point queries for the subdomain to the new authoritative DNS server.
  • Use Cases: Common in scenarios involving Global Server Load Balancing (GSLB), where DNS queries for a subdomain are delegated to a specialized system like F5 GTM, which dynamically resolves the best server based on proximity and load.

Example:

A company hosts example.com on an internal DNS server but wants to delegate gslb.example.com to F5 GTM to handle global traffic distribution. NS records are added in the internal DNS pointing gslb.example.com to F5 GTM’s DNS listeners. Now, queries for gslb.example.com are handled by F5 GTM, while example.com remains managed by the internal DNS.

4. DNS Forwarding

DNS Forwarding is used when an internal DNS server cannot resolve a query and forwards it to an external DNS server (e.g., public DNS resolvers like Google’s 8.8.8.8 or Cloudflare’s 1.1.1.1). This is commonly used in enterprise environments where internal DNS servers handle internal domains but need external DNS servers to resolve public domains.

Key Points:

  • Forwarding Queries: If an internal DNS server doesn’t have a record for an external domain (like google.com), it forwards the query to an external public DNS resolver.
  • Efficient Query Handling: Forwarding ensures that internal DNS servers don’t need to store records for external domains while still resolving public resources when needed.
  • Common in Enterprises: Internal DNS servers (like those in Active Directory) often use forwarders to resolve public domains outside the internal network.

Example:

An internal DNS server manages the domain internal.company.local. When a user queries google.com, the internal DNS forwards the request to Google’s public DNS server (8.8.8.8) to get the IP address of google.com.

5. Self-Hosted vs. Third-Party DNS Hosting

There are two main approaches for hosting authoritative DNS:

  1. Third-Party DNS Hosting: Services like GoDaddy, AWS Route 53, or Cloudflare offer DNS hosting. This is easy to set up, highly available, and widely used for public domains. These services act as the authoritative DNS server for your domain.

    Pros:

    • Simple and fast to configure.
    • High availability and distributed globally.
    • Advanced features like DDoS protection.

    Cons:

    • Limited control over DNS infrastructure.
    • Potential costs for advanced services.

  2. Self-Hosted DNS: In this case, the company hosts its own authoritative DNS servers, usually within its own infrastructure. This is common in large enterprises that need full control over their DNS configurations and data.

    Pros:

    • Full control over DNS infrastructure.
    • Enhanced security and customization.
    • Can manage both internal and external records directly.

    Cons:

    • More complex to manage and maintain.
    • Requires internal resources and expertise.
    • May lack the global reach of third-party providers.

Final Thoughts: Choosing the Right DNS Strategy

Understanding the different types of DNS (internal, authoritative, delegation) and how they interact is crucial for managing your domain’s DNS infrastructure effectively. Whether you're running an internal DNS for local name resolution or delegating subdomains to load balancers like F5 GTM, having the right DNS setup can improve performance, security, and scalability.

Organizations with complex needs often blend these DNS strategies—using internal DNS for local resources, authoritative DNS for public-facing domains, and delegation to handle specific subdomains via systems like F5 GTM for global load balancing.

By selecting the appropriate DNS setup, you can ensure that your network’s name resolution works efficiently, both inside and outside your organization.

This guide should help you navigate the world of DNS servers and delegation, making it easier to design an optimized DNS architecture that meets the unique needs of your organization.

Labels:

Comments

Post a Comment

Popular posts from this blog

Basic MPLS BGP and L3VPN Lab Setup

In this lab, we’ve set up a basic MPLS, BGP, and L3VPN environment, which is a great foundation for understanding how service providers build scalable networks. The lab uses the EVE-NG simulator along with Router IOS C7200-ADVENTERPRISEK9-M, Version 15.2(4)M8 to emulate a realistic MPLS environment. Below is a summary of the key components and roles of each router in the lab. MPLS Core Routers : The MPLS core consists of the routers responsible for label switching and forwarding customer traffic through the network: PE1 (Provider Edge 1) : Connects customer networks to the MPLS core and handles both MPLS and BGP routing. It also hosts VRF (Virtual Routing and Forwarding) instances for customers. PE2 (Provider Edge 2) : Functions similarly to PE1, connecting another customer network to the MPLS core. P1 (Core Router 1) and P2 (Core Router 2) : These routers serve as MPLS core routers and handle label switching but do not store or process customer routes directly. They simply f
Post a Comment
Read more

OSPF Adjacency Stuck in EXSTART on Cisco IOS XR – Issue and Solution

In a recent lab setup using Cisco IOS XR on EVE-NG, I faced a common but frustrating issue with OSPF adjacencies getting stuck in the EXSTART state. After spending considerable time troubleshooting interface MTUs and configurations, I discovered that the root cause was related to the virtual network interface type being used. This post outlines the issue, troubleshooting steps, and the eventual solution that got everything working. Issue: While configuring OSPF between two routers running Cisco IOS XR in my lab, OSPF adjacencies were getting stuck in the EXSTART state. I verified that interface configurations, MTU settings, and OSPF parameters were correct, but the problem persisted. I tried adjusting the MTU size, using the mtu-ignore command, and even checked for ACLs, but nothing seemed to resolve the issue. Troubleshooting Steps: MTU Settings: I started by verifying that both sides of the OSPF adjacency had matching MTUs. I used the default MTU and even tried different values wit
Post a Comment
Read more

How to Properly Clone an EVE-NG Lab with Configurations

Cloning labs in EVE-NG is a great way to duplicate setups and expand or experiment on a new copy without affecting the original lab. However, if not done correctly, the cloned lab may only copy the topology without configurations. In this guide, I’ll show you how to properly clone a lab in EVE-NG with all configurations using the EVE-NG GUI . Follow these steps to ensure that both the topology and router configurations are retained when cloning your lab. Steps to Clone an EVE-NG Lab with Configurations Save Running Configuration on All Devices In your original lab, make sure all devices have their configurations saved to NVRAM. Go into the CLI of each router and run the command: copy running-config startup-config Export All Configurations (CFGs) On the left sidebar in the EVE-NG Web UI , click on the "More Actions" option. Then select "Export all CFGs" . This step exports the configurations of all devices in the lab. Shutdown All Devices After exporting the confi
Post a Comment
Read more