Negative Caching

Negative caching (RFC 2308) means resolvers cache failures to find a record, such as NXDOMAIN (the name does not exist) or NODATA (the name exists but not for that record type), just as they cache positive answers.

Why it matters

It explains a classic frustration: you create a new record, but some users keep getting "not found". If a resolver looked up the name just before you added the record, it remembers the empty answer. The duration is taken from the SOA record in the negative response: the lower of the SOA's own TTL and its minimum field. A large minimum value can make a new record appear missing for hours. Positive answers use the record TTL instead.

Example

$ dig newhost.example.com A
;; status: NXDOMAIN
example.com. 900 IN SOA ns1.example.com. admin.example.com. (
    2026100501 7200 3600 1209600 300 )

Here the answer is cached for up to 300 seconds. After you add the record, wait that long, or query a different resolver to confirm.

Common mistakes

• Setting a very long SOA minimum value and forgetting it affects missing names.
• Testing a record before publishing it, which seeds the negative cache.
• Blaming propagation when the cause is a cached negative answer.

Related

• NXDOMAIN
• SOA record
• TTL
• DNS propagation

यह पेज सामान्य जानकारी है, जिसे हमारी संपादकीय टीम ने लिखा है और दस्तावेज़ीकरण बदलने पर अपडेट किया जाता है। सर्वर और प्रदाता अलग-अलग होते हैं, इसलिए बदलाव पहले सुरक्षित तरीके से जाँचें। देखें: संपादकीय नीति और अस्वीकरण.