TTL (Time-to-Live): Definition & Purpose

Time-to-Live (TTL) is a method that restricts how long data packets can remain online before a router discards them. It’s a critical component of the Internet, which is why we will explore it in detail in this article. Let’s start.

What does TTL (Time-to-Live) define?

TTL stands for “Time-to-Live.” The DNS record’s TTL setting determines how long a resolver must store a DNS query before it expires. Time-to-Live is frequently used to lighten the strain on your authoritative name servers and to expedite client DNS requests. This page discusses using Linux or Unix command-line parameters to determine a DNS record’s Time-to-Live.

How does it function?

All of the current website records that make up your entire site are stored on your authoritative domain server. Resolver servers verify your website’s name and its contents as the DNS website records travel and hop along the way (or packets). This method involves a lot of servers. When a record queries a server, the Time-to-Live count, which goes as high as 255, deducts 1 from the TTL number. The records continue to go across numerous servers and the Internet infrastructure to a final client (or workstation in the diagram above).

When the Time-to-Live count reaches “zero,” it means that 255 servers have handled the information. Unfortunately, the requested “packet” will be automatically deleted if this occurs. or ceases to “live.” This is referred to as TTL expiry, and if you tried to request a website, your browser would display the message “website not found.”

Recommendations to use TTL

The following significant considerations should be considered while specifying Time-to-Live:

  • The longer the TTL, the fewer times caching name servers must query authoritative name servers.
  • A longer TTL reduces a site’s perceived latency and its reliance on authoritative name servers.
  • The shorter the TTL, the faster the cached record will expire. This enables more frequent queries for the records.

To begin with, a longer Time-to-Live between an hour and 12 hours is acceptable if your website is hosted on a server that does not change IP for months. Fewer lookups would be required, and performance would be better and more consistent. You will need a TTL of between 1 and 10 minutes if you utilize our DNS Failover or Dynamic DNS services. Because dynamic DNS routinely changes your domain name’s IP address, and DNS failover may require you to be ready for the change.

What is “dhcp set ttl”?

On DHCP relay agents, the dhcp set ttl command is utilized. The Time-to-Live value of DHCP Discovery packets is, by default, decreased by 1 when a DHCP relay agent at Layer 3 forwards them. For example, assume that a DHCP Discovery message obtained by the DHCP relay agent has a TTL value of 1. The TTL value drops to 0 if the DHCP relay agent reduces it by 1. The next-hop routing device will discard the message because itsTime-to-Live value is 0. As a result, the DHCP relay agent forwarding the DHCP Discover message to the DHCP server is unsuccessful.

After the message is forwarded at Layer 3, use the dhcp set ttl command to set the Time-to-Live value of the DHCP Discovery message to a non-zero value to confirm that the DHCP server can receive the message provided by the client.


The Time-to-Live value is a crucial component that establishes the data’s validity time. It will indicate if the information is current or needs immediate updating. It facilitates data updating.