Bind updating serial number for zones
Time in seconds that a secondary name server should wait between zone file update checks.The value should not be so short that the primary name server is overwhelmed by update checks and not so long that propagation of changes to the secondary name servers are unduely delayed.Even if you configure your primary name server to send NOTIFY messages (which I will cover in a future article) to the secondary name servers whenever a change is made, you should never completely depend on this to ensure timely propagation of the changes, especially when using third-party secondary name servers.The decision to honor a NOTIFY message is entirely up to the secondary name server and some DNS servers do not support NOTIFY.A good retry value would be between 10 minutes (600 seconds) and 1 hour (3600 seconds), depending on the length of the Refresh Interval.Time in seconds that a secondary name server will treat its zone file as valid when the primary name server cannot be contacted.In the hosting industry, the Domain Name System (DNS) is one of the most critical pieces, right behind websites themselves.Without DNS, that website you've worked so hard on would be completely invisible.
Without a working DNS record, virtual websites are completely inaccessible.) But I've found that DNS is something that is not well understood by many website operators.Now if you control all of the authorative DNS servers for a domain (that is, the DNS servers that actually host the zone files and can answers queries for the domain as opposed to having to ask another DNS server), then with the exception of how long negative responses should be cached, these settings may not seem as important since you can force the secondary servers to update whenever needed.By if you are using third-party name servers which you do not control as your secondary name servers (such as Peer 1's Super DNS servers), then these settings are vitally important to how fast any changes are propagated.The basics of creating A records (which translate a hostname to an IP address) are simple enough, but when it comes to understanding how changes are propagated in DNS, this is often something of a mystery.There is a widely held belief that any change made the DNS zone file of a domain is instantly seen throughout the Internet. When advising that changes be made to a zone file to fix a problem, I routinely add the following caveat: Changes to a zone file are almost never instantaneous regardless of how despreate you are that they be instantaneous.