SOA Expire Value Out of Recommended Range

What Is the Cause of "SOA Expire Value Out of Recommended Range" Error?

When managing a network, understanding the SOA (Start of Authority) DNS record is crucial for IT administrators. This record is a key part of the DNS system, which is like the internet's address book. The SOA record holds important information about the domain, such as the primary name server, the email of the domain administrator, and various timers, including the Refresh, Retry, Expire, and Minimum TTL (Time to Live) values.

One of these timers, the Expire Value, plays a vital role in DNS health. It tells secondary servers how long to wait before considering the data outdated if they can't communicate with the primary server. According to RFC 1912, a set of guidelines for DNS settings, the recommended range for the Expire Value is between 1209600 to 2419200 seconds, which translates to 14 to 28 days. This range is designed to balance between allowing enough time for unforeseen outages and ensuring the data doesn't become too stale.

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The Risks of Setting SOA Expire Value Outside the Recommended 14-28 Day Range

However, problems arise when the SOA Expire Value is set outside this recommended range. If it's too short, DNS servers might not have enough time to recover from network issues, leading to unnecessary traffic and potential downtime. On the other hand, setting the value too high can cause outdated information to linger, leading to misdirected traffic and security vulnerabilities.

For example, an IT administrator might set an Expire Value like this in their DNS configuration:

$TTL 86400
@   IN  SOA (
    2023020501 ; Serial
    7200       ; Refresh
    900        ; Retry
    950400     ; Expire - 11 days, out of recommended range
    86400 )    ; Minimum TTL

In this case, the Expire Value is set to 950400 seconds (11 days), which is below the recommended minimum of 14 days. This setting could lead to potential issues if the primary server goes down for an extended period.

As you can see in the following screenshot, as a reference example, has Expire Value set to 1209600 which is exactly 14 days.

It's essential for IT administrators to adhere to the recommended settings, like those in RFC 1912, to maintain a robust and resilient DNS infrastructure. Regularly reviewing and adjusting these settings can help prevent disruptions and ensure efficient network operations.

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