Reverse Lookup Zone vs Forward Lookup Zone
Domain Name System (DNS) is a naming system that is used by any resource connected to internet. DNS translates domain names, which are more meaningful to humans, in to IP addresses associated with internet resources to locate them throughout the world. Each time an IP address is used, the DNS translates the name in to the corresponding IP address. Forward lookup zone holds host name to IP address relations. When a computer requests an IP address for a specific host name, the forward lookup zone is queried to get the result. On the other hand, Reverse lookup zone contains the IP address to host name mapping. When a computer requests a host name for a specific IP address, the reverse lookup zone is queried to get the answer.
What is forward lookup zone?
Forward lookup zone contains a mapping between host names and IP addresses. When a computer requests an IP address by providing a host name (that is more user friendly), the forward lookup zone is queried to find the IP address for the given host name. For example, when you type www.cnn.com in your browser, the forward lookup zone will be queried and the IP address 157.166.255.19 will be returned, which is actually the IP address of that site. When a forward lookup is sent to the DNS server, the DNS server searches for an A type resource record associated with the host name provided by the request. An A type resource is a DNS record that can be used to point the domain name and host names to a static IP address. If the DNS server finds a matching A type resource record, it will return that to the client, else it will forward the query to another DNS server.
What is reverse lookup zone?
Reverse lookup zone contains a mapping that relates IP addresses to host names. When a computer requests for a domain name by providing an IP address, the reverse lookup zone is queried to find the host name for the IP address given. For example, if a client wants to find the host name for the IP address 157.166.255.19, the reverse lookup zone will be queried and it will return the host name www.cnn.com. The reverse lookup zone contains PTR resource records. A PTR record allows doing a reverse lookup by pointing the IP address to a host/domain name. When doing reverse lookups, these PTR records are used to point to A resource records.
What is the difference between Reverse Lookup Zone and Forward Lookup Zone?
The main difference between forward lookup zone and reverse lookup zone is that forward lookup zone is used to resolve forward lookup queries where the client requests an IP address by providing the host name, while reverse lookup zone is used for resolving reverse lookup queries where a client requests a host name by providing an IP address. The forward lookup zone contains A type resource records that can point out an IP address for a given host name. The reverse lookup zone contains PTR records that can point out a host name for a given IP address.