The Domain Name Service, or DNS, is what makes IP networking work for humans. It is a simple yet elaborate technology which permits the use of human-readable host and domain names rather than cryptic IP addresses. It is one of the cornerstones of the Internet and an important element of any Local Area Network. It is such an important part of networking that a DNS failure can render a whole network unusable. To prevent or reduce DNS service outages, monitoring and troubleshooting tools are available. Today, we’ll help you see clearly through the maze of available products and tools and review some of the best DNS server monitoring and troubleshooting tools we could find.
Before we get to the actual reviewing of the best products we’ve found, we’ll cover some basic background information. We’ll start off by trying to explain, in as non-technical terms as possible, what DNS is and how it operates. That will help better understand the need for monitoring DNS server and how to troubleshoot its issues. Talking about troubleshooting, it will be our next topic and we’ll have a look at what happens when things go wrong with DNS. Finally, we’ll get to the core of our subject and briefly review the best tools we could find and describe each one’s best features.
DNS in a Nutshell
To relieve humans of the burden of addressing them using cryptic IP addresses, each computer has a hostname in addition to its IP address. Years ago, when the Internet was comprised of a very limited number of interconnected computers, each computer connected to the Internet had a text file named “hosts” which contained the hostname to IP address correspondence of every other computer on the Internet.
It worked fine as long as there were a limited number of interconnected computers. Every time a new computer was brought up, the “hosts” file of every computer on the Internet had to be updated. As more and more computers joined the Internet, it soon became apparent that some better way of distributing the hostname to IP address correspondence had to be devised.
This is why DNS was created. Simply put, DNS is basically a distributed version of the “hosts” file which can resolve the IP address of any hostname. DNS is a distributed system where each local administrator is responsible for the data about the hosts he manages. Through a process of forwarding and delegation, any DNS server can ultimately find the corresponding IP address of any combination of hostname and domain name. This combination, by the way, is what we refer to as a Fully Qualified Domain Name, or FQDN.
Organizations typically maintain one or more local DNS servers which are responsible for resolving IP addresses of local networked resources. These servers will forward any request they can’t resolve to their forwarding server, a public DNS server on the Internet. Without going too technical on the precise details of how they do that, rest assured that each public DNS server can ultimately resolve any public FQDN to its corresponding IP address. By extension, your local DNS server can do that too since it forwards requests he can’t resolve to a public DNS server.
As good as the concept of DNS is, it is not without any shortcomings. One of its primary drawbacks is that with all the forwarding of requests from name server to name server, resolving an IP address can end up taking a while. This effect is somewhat mitigated by the extensive use of caching. Whenever a DNS server fetches a record indicating a correspondence between a name and an address, no matter if it’s for itself or on behalf or another server, it will cache that record. The next time the same information is requested, it won’t have to fetch it from another server and it will use the cached version. Caching is not eternal though. It is configurable and typically lasts between a few minutes and a few days. Sooner or later, cached information will expire and servers will need to fetch fresh record from other servers.
DNS Monitoring – What Is It All About?
Just like any monitoring, there are several things one can monitor about DNS server. A DNS server is, first and foremost, a server. It runs an operating system and the DNS server part is actually nothing more than a service running on that server. In that context, monitoring a DNS server is not any different from monitoring any other server and the applications and services running on them.
You want your DNS servers to perform within an acceptable range. It can’t, for instance, take a minute to resolve an FQDN to an IP address. However, DNS server response time is not a parameter that is often monitored as there are simply too many external factors affecting it. However, some tools will perform that kind of monitoring as it can have some value when monitoring a local server.
But the simplest kind of monitoring that you can perform on a DNS server is just making sure that it is responding to DNS queries. This is precisely what many cloud-based DNS monitoring services will do.
When Things Go Wrong With DNS
The Domain Name Service’s architecture is robust and outages are quite infrequent. However, when dealing with internal DNS, the one that is used to resolve local hostnames, there is often a single server. If that sole server starts acting up, you better have testing tools readily available as it can render a network virtually unusable.
Troubleshooting DNS architecture is also a common task, especially when setting up new servers. You’ll want to make sure that the forwarding servers are properly configured and that whatever required delegation is also correctly configured. As you’re about to see, there are tools made especially for that.
The Best DNS Server Monitoring and Troubleshooting Tools
As we indicated above, monitoring a DNS server is not much different from monitoring any other server. Don’t be surprised, then, to see some server monitoring tools on our list. We’ll review those with an emphasis on their DNS capabilities, though. Our list also contains dedicated DNS testing and troubleshooting tools as well as cloud-based DNS monitoring services.
The Server And Application Monitor from SolarWinds—one of the best-known publisher of network and system administration tools—is self-described as a “Server monitoring software built to find and resolve application problems”. In summary, this tool allows you to monitor any application, any server, anywhere. You can use it to proactively monitor the performance, capacity, and health of Linux and Windows apps across data centers, remote offices, and in the cloud.
- FREE TRIAL: SolarWinds Server and Application Monitor
- Official Download Link: https://www.solarwinds.com/server-application-monitor/registration
Since it’s on this list, you can imagine that DNS monitoring is available with this tool. Indeed, it is known to deliver a top-notch DNS monitoring experience. The SolarWinds Server and Application Monitor analyzes the response speed of a DNS server by assessing how fast the server responds to a record query and comparing the response against a list of IP addresses. If the response time is lagging behind other IP addresses, it is flagged as a problem. In addition, without requiring any manual configuration, the tool will notify you when a DNS server receives an unusually high number of requests, allowing you to take action quickly.
The SolarWinds Server and Application Monitor is a comprehensive server monitoring platform for Microsoft applications, systems, hypervisor, and SaaS products. It is also a great product for monitoring cloud-based infrastructures such as Microsoft Azure and AWS. All this is available from the same dashboard as your on-premises applications and systems. Talking about the dashboard, it will let you monitor over 1200 vendor applications, servers, databases, and storage, all from a single, easy-to-use, customizable web interface. The monitoring tool provides automated discovery and mapping of applications and infrastructure. It also has customizable monitoring templates, and pre-built alerts and reports.
Prices for the SolarWinds Server and Application Monitor are based on the number of components, nodes, and volumes monitored, starting at $2 995 for 150 monitors. Like most other SolarWinds products, a free 30-day trial version is available for download, allowing you to give it a test run before purchasing it.
Next on our list is another excellent tool from SolarWinds called DNS Audit. This tool is only available as a bundle with the SolarWinds Engineer’s Toolset, a pack of some sixty different tools for network and system administration.
The SolarWinds DNS Audit tool is exactly what its name would lead you to believe. It primarily made for network administrators who manage and configure their DNS manually. That is without using an IP Address Management System. It is not bloated with features and what it does is pretty simple but the benefits are real.
- FREE Trial: SolarWinds Engineer’s Toolset
- Official Download Link: https://www.solarwinds.com/engineers-toolset/dns-audit/
This tool will scan a specific range of IP address and issue reverse-DNS queries for each address. Reverse DNS is the process of interrogating a DNS server to get the hostname corresponding to an IP address instead of the contrary. A properly configured DNS server should have a reverse DNS record for each forward record it contains.
Once the tool has finished resolving each IP address into a hostname, it will try to resolve each hostname to an IP address and it will report on any record where a mismatch between the reverse and forward resolution is found. The result of the audit is shown in tabular form with one line for each IP address scanned.
Next, we have another DNS troubleshooting tool from SolarWinds called the DNS Structure Analyzer. It is another component of the SolarWinds Engineer’s Toolset. This tool is quite different from the previous one in what it does and how it operates. It will discover and create visual diagrams of the hierarchical DNS structure of your organization’s DNS resource records. This includes root servers, name servers, global top-level domain servers, cName pointers, and authoritative address servers. Another use for this tool is to help you distinguish the relationships between multiple name servers and target IP addresses by using the DNS structure diagram. Furthermore, redirections from one DNS server to another are graphically displayed.
The SolarWinds DNS Structure Analyzer is a highly task-specific tool. As such, it might not be for everyone. But those who have a need for this type of tool couldn’t ask for anything more. This excellent tool is part of the Engineer’s Toolset free trial. Perhaps you should give it a try and see for yourself if you have a need for it.
Other Features Of the SolarWinds Engineer’s Toolset
The two previous tools were part of the SolarWinds Engineer’s Toolset which includes many more great tools. It contains a mix of a few free tools which are also available individually and many exclusive tools which can’t be obtained otherwise. All the tools are easily accessed from a centralized dashboard. Among the different tools you’ll find, there’s Ping Sweep and TraceRoute which can be used to perform network diagnostics and help resolve complex network issues quickly. Security-conscious network administrators will appreciate a few tools that can be used to simulate attacks on your network and help identify vulnerabilities.
- FREE TRIAL: SolarWinds Engineer’s toolset
- Official Download Link: https://www.solarwinds.com/engineers-toolset/
The SolarWinds Engineer’s Toolset also includes a few monitoring and alerting tools including one which will monitor your devices and raise alerts when it detects availability or health issues. This will often give you enough time to react before users even notice the problem. To complete an already feature-rich suite of tools, configuration management and log consolidation tools are also included.
Here’ a list of some of the most useful tools you’ll find in the SolarWinds Engineer’s Toolset besides DNS audit and DNS Structure Analyzer.
- Port Scanner
- Switch Port Mapper
- SNMP sweep
- IP Network Browser
- MAC Address Discovery
- Ping Sweep
- Response Time Monitor
- CPU Monitor
- Interface Monitor
- Router Password Decryption
- SNMP Brute Force Attack
- SNMP Dictionary Attack
- Config Compare, Downloader, Uploader, and Editor
- SNMP trap editor and SNMP trap receiver
- Subnet Calculator
- DHCP Scope Monitor
- IP Address Management
- WAN Killer
The SolarWinds Engineer’s Toolset—including the DNS Audit and DNS Structure Analyzer tools sells for $1495. When considering that there are some 60 different tools included in that bundle, it’s a very reasonable price. While there are simply too many tools in the SolarWinds Engineer’s Toolset to mention them all, a free 14-day trial available so your best bet might be to download the bundle and see for yourself what it can do for you.
4. PRTG With DNS Sensor
The Paessler Router Traffic Grapher (PRTG) is, at its base, a bandwidth monitoring tool. It is a feature-rich product which can monitor much more than bandwidth, though. More about that in a moment. The software comes with a choice of a native Windows enterprise console, an Ajax-based web interface and mobile apps for Android, iOS, and Windows Phone. The platform can perform its duties using SNMP, WMI, NetFlow, Sflow, and several more technologies.
But the monitoring possibilities of PRTG are almost endless thanks to its sensors—you can think of them as extensions of the product—which are available for almost any purpose. Of particular interest today is the tool’s dedicated DNS sensor which runs DNS monitoring automatically in the background. The DNS sensor you gives you an overview of both live and historical data. DNS query response time is displayed on a colour-coded dial that is easy to read. It can also display historic for the past 2 days, 30 days, or 365 days.
PRTG is available in a free version that will limit your monitoring to no more than 100 sensors. Each parameter you want to monitor counts as one sensor. For example, monitoring bandwidth on each port of a 48-port switch will require 48 sensors. Each instance of the DNS sensor also counts as one. For more than 100 sensors you’ll need a paid license which starts at $1600 for up to 500 sensors, including the first year of maintenance. A free 30-day trial version is also available.
Dotcom-Monitor is one of the simplest DNS monitoring services on the market. It works by assessing request times and instantly responding with a DNS trace and an alert if a problem is found. The DNS trace it produces shows the full path of the connection including details like Resolving Host, Duration, Start Time, Addresses and Aliases.
About the alerting features of the product, alerts will show you what the problem is and provide you with links to view the trace straight from the alert window. As simple as it is Dotcom-Monitor is impressive in how many different types of records can be monitored. Most record types including A, AAAA, NS, CNAME, SOA, TXT, MX, PTR, and SPF are supported by the product. This diversity of record types can be a big help when it comes to troubleshooting because it gives you much more information to work with.
Dotcom-Monitor is available in several packages with varying feature level. DNS monitoring is only included in the top-tier Internet Infrastructure plan which starts at $39.99/month. A free 30-day trial is also available.
UpTrends is a free DNS lookup tool which you can use for DNS monitoring. The tool will monitor key records such as A, AAAA, SOA, TXT, and MX. Tests can be performed from 184 regional checkpoints distributed across the globe. A useful feature that can make it easy to identify any regional problem.
UpTrends is not limited to the basic records. It will, for instance, monitor SOA serial numbers to see if and when a DNS entry changes. This allows you to spot subtle changes that you’d likely miss if you were just checking the standard records.
This feature-rich tool also includes reports and alerts. It will send daily reports showing the status of your DNS service. These reports can help you see if there are any problems. As for the tool’s alerting features, they will ensure you’re notified immediately in the event that something that needs you to take action happens.