It is possible to do this. At one point it was up in the air a bit until 4592 clarified that it should be supported. Just because it is possible doesn’t mean it is supported by all DNS providers. For example, GoDaddy won’t let you set up a wildcard in a CNAME record. In terms … Read more
The whole idea behind the MX record is to specify a host or hosts which can accept mail for a domain. As specified in RFC 1035, the MX record contains a domain name. It must therefore point to a host which itself can be resolved in the DNS. An IP address could not be used … Read more
The commands dig and host should be what you’re looking for 😉 On *nix systems, you can use this command: dig -x [address] Alternatively, you can add +short at the end of the dig command to output only the DNS result. There’s also nslookup on both *nix and Windows systems for reverse DNS requests.
It depends on whether you want to delegate hosting the subdomain off to a different DNS server (or to the same server, but in a different zone file). You delegate a zone when you want some other entity to control it, such as a different IT department or organization. If you do, then you need … Read more
Yes, the number there is the number of seconds left until that record expires (providing we’re not querying the authoritative nameserver). Obviously with a CNAME there’s a level of redirection, so the TTL for the A record it points to in this case may be important as well. If you wait a couple of seconds … Read more
RFC 1035 defines the format of a DNS zone file. … on page 35 you’ll find: @ A free standing @ is used to denote the current origin. This means that @ is a shortcut for the name defined with $ORIGIN. You can find more information on $ORIGIN here, which is an excerpt from Pro … Read more
You can use the @ syntax to look up the domain from a particular server. If the DNS server is authoritative for that domain, the response will not be a cached result. dig @ns1.example.com example.com You can find the authoritative servers by asking for the NS records for a domain: dig example.com NS
CNAME records were originally created to allow multiple names that provide the same resource to be aliased to a single “canonical name” for the resource. With the advent of name based virtual hosting, it has instead become commonplace to use them as a generic form of IP address aliasing. Unfortunately, most people who come from … Read more
Basically, it’s what the name says it is. An authoritative answer comes from a nameserver that is considered authoritative for the domain which it’s returning a record for (one of the nameservers in the list for the domain you did a lookup on), and a non-authoritative answer comes from anywhere else (a nameserver not in … Read more
Since the previous answers to this question were written, there have been a couple of RFCs that alter the guidance somewhat. RFC 6761 discusses special-use domain names without providing specific guidance for private networks. RFC 6762 still recommends not using unregistered TLDs, but also acknowledges that there are cases where it will be done anyway. … Read more