What is a TTL in DNS and how should I configure it?
A TTL (Time to Live) in DNS is a numerical value that determines how long DNS records remain cached on servers and devices before they expire. When you configure DNS TTL settings, you control how frequently other servers need to check for updates to your domain's DNS records. Lower TTL values mean more frequent updates but increased server queries, while higher values reduce network traffic but slow down propagation of DNS changes.
Understanding DNS TTL fundamentals
DNS TTL acts as an expiration timer for cached DNS information across the internet. When someone visits your website, their device queries DNS servers to translate your domain name into an IP address. These servers store this information temporarily based on your TTL setting.
The Domain Name System relies on caching to function efficiently. Without TTL values, DNS servers would constantly query authoritative servers for the same information, creating unnecessary network congestion. TTL prevents this by telling caching servers exactly how long they can trust stored DNS data.
DNS infrastructure uses TTL as a fundamental caching mechanism. Every DNS record type, including A records, CNAME records, and MX records, carries its own TTL value measured in seconds.
What is TTL in DNS and why does it matter?
TTL in DNS controls how long DNS records stay cached before servers must refresh them from authoritative sources. This directly impacts both DNS propagation speed and server performance across the internet.
When you change DNS records, the TTL value determines how quickly these changes spread globally. A TTL of 300 seconds means cached records expire after 5 minutes, forcing servers to fetch updated information. Higher TTL values like 86400 seconds (24 hours) mean changes take much longer to propagate worldwide.
DNS TTL matters because it affects your website's availability during DNS changes. Planning server migrations or switching hosting providers requires careful TTL management to minimise downtime and ensure smooth transitions.
How does DNS TTL affect website performance?
DNS TTL significantly impacts website loading speeds through its effect on DNS query frequency. Higher TTL values reduce the number of DNS lookups required, leading to faster page loads for returning visitors.
When TTL values are too low, users experience slower website performance because their devices must repeatedly query DNS servers. Each DNS lookup adds latency to the connection process, particularly noticeable on mobile networks or slower internet connections.
Server load also depends on your TTL configuration. Lower TTL settings increase the number of queries hitting your authoritative DNS servers, potentially causing performance bottlenecks during high traffic periods. Balancing performance with flexibility requires choosing TTL values that suit your specific needs.
What are the best TTL values for different DNS records?
Optimal TTL settings vary significantly depending on the DNS record type and your operational requirements. Different records serve different purposes and change at different frequencies.
| Record Type | Recommended TTL | Use Case |
|---|---|---|
| A Records | 300-3600 seconds | Standard website hosting |
| CNAME Records | 3600-14400 seconds | Subdomain aliases |
| MX Records | 3600-86400 seconds | Email server configuration |
| TXT Records | 300-3600 seconds | Verification and security |
A records pointing to web servers benefit from moderate TTL values between 5 minutes and 1 hour. This provides reasonable caching while allowing relatively quick updates when needed. MX records can use higher TTL values since email server changes happen infrequently.
How do you configure TTL settings properly?
Configuring TTL settings involves accessing your DNS management interface and modifying the TTL field for each DNS record. Most DNS management platforms display TTL values in seconds alongside other record details.
Start by logging into your DNS provider's control panel and locating your domain's DNS records. Look for a column labelled "TTL" or "Time to Live" next to each record entry. Click the edit button for the record you want to modify.
Enter your desired TTL value in seconds. Common values include:
- 300 seconds (5 minutes) for frequently changing records
- 3600 seconds (1 hour) for standard configurations
- 86400 seconds (24 hours) for stable, rarely changing records
Save your changes and allow time for the new TTL to take effect. Remember that the current TTL value determines how long it takes for your new TTL setting to propagate fully.
Key takeaways for DNS TTL optimisation
DNS optimisation through proper TTL configuration balances performance, flexibility, and reliability. Lower TTL values provide faster change propagation but increase server load and DNS query frequency.
Avoid common mistakes like setting extremely low TTL values unnecessarily or forgetting to reduce TTL before planned DNS changes. Plan ahead by lowering TTL values 24-48 hours before major DNS modifications to ensure smooth transitions.
Monitor your DNS performance regularly and adjust TTL values based on your actual needs. Websites with frequent DNS changes benefit from lower TTL values, while stable configurations can use higher values for better performance.
Understanding DNS TTL configuration helps you maintain optimal website performance whilst retaining the flexibility to make necessary changes. At Falconcloud, we provide comprehensive DNS management tools that make configuring and monitoring your TTL settings straightforward, ensuring your DNS infrastructure performs reliably across our global network.
