Introduction
DNS, or the Domain Name System, is often a difficult component to get right when learning how to configure websites and servers. While most people will probably choose to use the DNS servers provided by their hosting company or their domain registrar, there are some advantages to creating your own DNS servers.
In this guide, we will discuss how to install and configure the Bind9 DNS server as a caching or forwarding DNS server on Ubuntu 14.04 machines. These two configurations both have advantages when serving networks of machines.
Prerequisites and Goals
To complete this guide, you will first need to be familiar with some common DNS terminology. Check out this guide to learn about some of the concepts we will be implementing in this guide.
We will be demonstrating two separate configurations that accomplish similar goals: a caching and a forwarding DNS server.
To follow along, you will need to have access to two computers (at least one of which should be an Ubuntu 14.04 server). One will function as the client and the other will be configured as the DNS server. The details of our example configuration are:
| Role |
IP Address |
| DNS Server |
192.0.2.1 |
| Client |
192.0.2.100 |
We will show you how to configure the client machine to use the DNS server for queries. We will show you how to configure the DNS server in two different configurations, depending on your needs.
Caching DNS Server
The first configuration will be for a caching DNS server. This type of server is also known as a resolver because it handles recursive queries and generally can handle the grunt work of tracking down DNS data from other servers.
When a caching DNS server tracks down the answer to a client’s query, it returns the answer to the client. But it also stores the answer in its cache for the period of time allowed by the records’ TTL value. The cache can then be used as a source for subsequent requests in order to speed up the total round-trip time.
Almost all DNS servers that you might have in your network configuration will be caching DNS servers. These make up for the lack of adequate DNS resolver libraries implemented on most client machines. A caching DNS server is a good choice for many situations. If you do not wish to rely on your ISPs DNS or other publicly available DNS servers, making your own caching server is a good choice. If it is in close physical proximity to the client machines, it is also very likely to improve the DNS query times.
Forwarding DNS Server
The second configuration that we will be demonstrating is a forwarding DNS server. A forwarding DNS server will look almost identical to a caching server from a client’s perspective, but the mechanisms and work load are quite different.
A forwarding DNS server offers the same advantage of maintaining a cache to improve DNS resolution times for clients. However, it actually does none of the recursive querying itself. Instead, it forwards all requests to an outside resolving server and then caches the results to use for later queries.
This lets the forwarding server respond from its cache, while not requiring it to do all of the work of recursive queries. This allows the server to only make single requests (the forwarded client request) instead of having to go through the entire recursion routine. This may be an advantage in environments where external bandwidth transfer is costly, where your caching servers might need to be changed often, or when you wish to forward local queries to one server and external queries to another server.
Install Bind on the DNS Server
Regardless of which configuration choice you wish to use, the first step in implementing a Bind DNS server is to install the actual software.
The Bind software is available within Ubuntu’s default repositories, so we just need to update our local package index and install the software using apt. We will also include the documentation and some common utilities: Continue reading How To Configure Bind as a Caching or Forwarding DNS Server on Ubuntu 14.04 →
