Understanding DNS and its working is one of the most difficult computer engineering subject and yet most experienced network administrators struggle in this topic when it comes to DNS zone file writing. (see RFC 1912 section 2.3) In the above example we are mapping each NS records to IP address (A record) thus binding nameservers to IP (that is glue them).
Before I proceed with this article, the following are the MOST IMPORTANT points you should remember as otherwise you wouldnt understand bit. An A Record must ALWAYS contain IP address (map host to IP) Whenever you specify A record it must contain IP address on the Right side. A nameserver which gives non-authoritative answer is usually called 'LAME'. An example of lame delegation is ns1.is configured to have zone information about domain but ns2.was not configured properly and does not have any information about the domain.
In addition to being able to resolve names to a private namespace or speed up name resolution to a public namespace without the use of Conditional Forwarders or Stub Zones.
When a Secondary DNS server is configured it will request a zone transfer from a DNS Server maintaining the Master database for a zone.
Specifically, it will push forward (A) and reverse (PTR) lookup entries.
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A Secondary Zones allows an organization to provide fault tolerance and load balancing to internal names.DNS (Domain name system) may not be known to most people who use the Internet but it is the real invisible force driving the Internet without which everyone would be seeing numbers and IPs. Use the DOT in the end, whenever you specify a domain name in the DNS zone file.The whole meaning of domain names exists today just because of DNS. This DOT is so important and if you forget this you will have nightmares with your dns configuration. simply because it tells to start query from root servers (denoted by dot) 5.If the name server receiving an authorized update message is not the primary master for the zone, it forwards the update "upstream" to its master server, a process referred to as "update forwarding." If this next server, in turn, is a slave for the zone, it also forwards the update upstream.Only the primary master name server for a zone, after all, has a "writable" copy of the zone data; all of the slaves get their copies of the zone data from the primary master, either directly or indirectly (through other slaves).