DNS is the phone book of the internet. When it breaks, nothing else matters — your servers can be perfectly healthy and your site will be completely unreachable. Yet DNS is one of the least-monitored layers in most UK business IT stacks.
Why DNS fails without warning
DNS failures happen at the registrar, at the hosting provider, and in your own configuration — and none of these events produce an error in your application logs. Common causes include: domain renewal lapsing (the registrar disables DNS), nameserver changes that propagate incorrectly, CDN or DNS provider outages, and manual DNS record edits that introduce typos. All of these are invisible to HTTP and TCP checks until the DNS record itself fails to resolve.
What DNS monitoring checks
A DNS check queries a nameserver for a specific record — typically an A record or CNAME — and verifies it returns the expected IP address or alias. If the query times out, returns no records, or returns an unexpected value, the check fails. This catches both total resolution failures and subtle changes where a misconfigured edit has changed where your domain points.
DNS TTL and propagation
DNS changes do not take effect immediately. TTL (Time To Live) values on your records determine how long resolvers cache the old value. A TTL of 3600 means changes take up to an hour to propagate globally. Monitoring DNS from a fixed resolver (like 8.8.8.8) gives you a consistent view of what most of the internet sees, but propagation means there can be a window where some users see the old record and others see the new one.
Adding DNS checks to your status page
In VP Watchtower, add your domain as a DNS check service. The monitor queries for an A record on your hostname and reports whether resolution succeeds. If you recently migrated hosting providers or changed nameservers, add a DNS check immediately to confirm propagation has completed correctly before you declare the migration done.