Learn why DNS Has Started Failing Intermittently on Linode and how to fix It. Our Linode Support team is here to help you with your questions and concerns.
Why DNS Has Started Failing Intermittently on Linode and How to Fix It
DNS plays a key role in translating human-readable domain names into IP addresses that computers use to communicate. However, DNS issues can disrupt connectivity and lead to unsatisfied queries. Hence, we need to understand the causes and resolve these problems as soon as possible.
Today, we will look at some of the common causes of DNS issues, tools for troubleshooting, and best practices for maintaining a stable DNS environment.
An Overview:
Causes of Unsatisfied Queries in DNS
Here are some of the causes behind unsatisfied queries:
- A lack of a viable network circuit path from the client to the specified DNS server.
- The specified DNS server may not have the required credentials to resolve the query.
- Cached information on the DNS server might be out of date, leading to incorrect responses.
- The DNS server may have no upstream connectivity to a TLD (Top-Level Domain) server.
Our Experts would like to point out that there are several tools across Windows, macOS, and Linux to help us troubleshoot these DNS problems. Most of these tools focus on tracing network circuits to DNS resolvers or querying DNS servers for accurate responses.
Tools for DNS Troubleshooting
The most popular DNS query tool beyond `nslookup` is `dig` (Domain Information Groper).
On Windows, `dig` must be downloaded as part of the BIND package. It also includes an optional DNS server. On macOS and Linux, `dig` is typically included by default.
The `dig` command allows users to query specific DNS records, such as:
- MX (Mail Exchange) records for email services.
- A records for domain resolution.
- TXT records for specific information.
- Other records found in the SOA (Start of Authority).
Some of the key `dig` options include:
- `+trace`: Traces DNS queries to the SOA.
- `ANY`: Retrieves all available records instead of the default A record.
- `+f `: Specifies a file containing hosts to query.
The Role of DNS Registrars and Resolvers
Every domain registered in DNS has an associated registrar. This registrar maintains records of ownership, though only the IP addresses of its nameservers must be made public. Nameservers are the guardians of DNS for TLDs and provide critical domain information.
Organizations hosting domains often operate their own nameservers and serve as the SOA for their domain and subdomains. TLD resolvers like `.com`, `.net`, and `.org` are highly secure and only accessible through DNS Security Extensions (DNSSEC), ensuring authentication and security.
Some hosting providers, like Linode, may utilize CDNs to manage IP and DNS access.
The Importance of the Hosts File
Before attempting to resolve a DNS query, operating systems look at the hosts file. The hosts file is located at:
- Windows: `\system32\hosts`
- macOS/Linux: `/etc/hosts`
The hosts file is canonical, overriding all other resolvers. It can be used to:
- Block access to specific sites for security purposes.
- Serve as a private DNS to control system behavior.
- Prevent typos from redirecting users to malicious sites.
When diagnosing DNS issues, it is a good idea to inspect the hosts file using a text editor to ensure no improper entries are interfering with DNS resolution.
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Conclusion
DNS issues are often caused by simple problems such as typos or network outages, which may initially appear as DNS failures. Verifying the network path and resolver accuracy resolves many such outages. Misconfigurations, particularly incorrect default DNS settings, should also be checked.
In brief, our Support Experts demonstrated why DNS Has Started Failing Intermittently on Linode and how to fix It.
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