Domain Name System (DNS) is a name resolution service that provides a naming system for computers, services, and other resources in the network. The DNS Server resolves computer names or other hostnames to IP addresses and IP addresses to computer names or other hostnames.
DNS Zones and Records
A DNS zone is the specific portion of a DNS namespace hosted on a DNS server and it contains resource records. The DNS records contain the information that DNS servers send in response to DNS requests. if the DNS server doesn’t have the requested information, it can forward DNS requests to another DNS server. Forward lookup zones stored different resource records, but the most common record is the host record. A host record is used to resolve a hostname to an IP address. Reverse lookup zones are used only for resolving an IP address to a name. All forward lookup and reverse lookup DNS zones contain SOA and NS Records. Start of authority (SOA) Contains configuration information for the zone, including the name of the primary DNS server and how often secondary servers should be synchronized. There’s one SOA record per zone. Name server (NS) Identifies a DNS server for the domain. There’s one NS record for each DNS server that has a copy of the zone.
Resource records in forward lookup zones
| Host (A) | A record used to resolve a name to an IPv4 address |
| Host (AAAA) | AAA record used to resolve a name to an IPv6 address |
| Alias (CNAME) | CNAME record used to resolve a name to another name |
| Service location (SRV) | SRV record used by applications to identify the location of servers hosting that application. For example, AD DS uses SRV records to identify the location of domain controllers and related services |
| Mail exchanger (MX) | MX record used to identify email servers for a domain |
| Text (TXT) | TXT Record used to store arbitrary strings of information in DNS |
Resource records in reverse lookup zones
| Pointer (PTR) | PTR record used to resolve an IP address to a name |
Primary Zone, Secondary Zone and Stub Zone
Primary Zone: This is the main zone and has a read/write copy of the zone data. All changes to the zone are made in the primary zone and are replicated in the secondary zones.
Secondary Zone: A secondary Zone is a read-only copy of the primary zone. This zone cannot process updates and can only retrieve updates from the primary zone. This zone can answer DNS name resolution queries from client’s nodes, this helps reduce the workload on the primary zone. Secondary zones cannot be active directory integrated.
Stub Zone: Stub zones are like secondary zones but only store partial zone data. These zones are useful to help reduce zone transfers by passing the requests to authoritative servers. These zones only contain the SOA, NS, and A records.
