The BIND DNS daemon caches a mapping of domain names to IP addresses, as does a resolver library.
Most prominently, it translates more readily memorized domain names to the numerical IP addresses needed for locating and identifying computer services and devices with the underlying network protocols.
The most common types of records stored in the DNS database are for Start of Authority (SOA), IP addresses (A and AAAA), SMTP mail exchangers (MX), name servers (NS), pointers for reverse DNS lookups (PTR), and domain name aliases (CNAME).
An often-used analogy to explain the Domain Name System is that it serves as the phone book for the Internet by translating human-friendly computer hostnames into IP addresses.
The glue records are address records that provide IP addresses for ns1.example.org.
The resolver uses one or more of these IP addresses to query one of the domain's authoritative servers, which allows it to complete the DNS query.
The DNS stores IP addresses in the form of domain names as specially formatted names in pointer (PTR) records within the infrastructure top-level domain arpa.
Hostnames and IP addresses are not required to match in a one-to-one relationship.
Alternatively, a single hostname may resolve to many IP addresses to facilitate fault tolerance and load distribution to multiple server instances across an enterprise or the global Internet.
DNS serves other purposes in addition to translating names to IP addresses.
The DNS is used for efficient storage and distribution of IP addresses of blacklisted email hosts.
The CLASS of a record is set to IN (for Internet) for common DNS records involving Internet hostnames, servers, or IP addresses.
A DHCP server enables computers to request IP addresses and networking parameters automatically from the Internet service provider (ISP), reducing the need for a network administrator or a user to manually assign IP addresses to all network devices.
DHCP is based on BOOTP but can dynamically allocate IP addresses from a pool and reclaim them when they are no longer in use.
A DHCP server can manage IP settings for devices on its local network, e.g., by assigning IP addresses to those devices automatically and dynamically.
The DHCP server manages a pool of IP addresses and information about client configuration parameters such as default gateway, domain name, the name servers, and time servers.
Depending on implementation, the DHCP server may have three methods of allocating IP addresses: DHCP is used for Internet Protocol version 4 (IPv4) and IPv6.
For those hosts which cannot accept unicast packets before IP addresses are configured, this flag can be used to work around this issue.
However, DHCP servers can also provide IP addresses for multiple subnets.
As of 2018, DHCP remains widely used for automatic assignment of IP addresses.