A common value is one week, or 604,800. Other name servers can cache any data from this server for at least this many seconds, unless a particular resource record overrides this value. A common value is one day, or 86,400. Address records are the bread and butter of a name server. These are the resource records that map a host name to an IP address.
Aliases make it easier to move services such as Web servers to other hosts.
A mail exchange record providing the name of a mail server for a particular domain. In addition to the domain name and a mail server for that domain, the record also includes a preference. If a domain has more than one mail exchange record, first priority is given to the mail exchange server with the lowest preference value. A name server record lists the authoritative name servers for a domain or subdomain. Most DNS lookups provide a domain name and request an IP address.