DNS History - FAQ

Questions:

Q1: Why do I see gaps in the dates for the same record?

Q2: A host name is missing from dnshistory?

Q3: Why do I only see records listed once when they are listed multiple times in the zone file?

Q4: How often do you check my domains DNS records?

Q5: Why do you list (sub)domains that don't exist?

Answers:

Q1: Why do I see gaps in the dates for the same record?
A1: We poll domains based on their popularity and some domains do not get polled daily, if during the days we haven't polled a change occurs we don't know when it changed which results in gaps.

Q2: A host name is missing from dnshistory?
A2: We only list host names with characters a-z, 0-9 and '-'. If you still feel we are missing a host name please add it via the Suggest domain form.

Q3: Why do I only see records listed once when they are listed multiple times in the zone file?
A3: We only list unique records, i.e. if the response for "A" records includes "10.0.0.1, 10.0.0.2, 10.0.0.1" we will only list "10.0.0.1,10.0.0.2" and not the repeated "10.0.0.1" entry.

Q4: How often do you check my domains DNS records?
A4: We aim to check every domain at least once per month and the minimum interval between checks is 24 hours. We also check the serial provided in the SOA to determine if we need to re-check the other records which cuts down the number of requests for (sub)domains that haven't changed since the last poll.

Q5: Why do you list (sub)domains that don't exist?
A5: We list (sub)domains that are referred to by other domains and this includes those that don't exist (Subject to A2 rules). We also list old (sub)domains that might no longer exist.