DNS forwarders are used to redirect DNS queries for a specific domain or set of domains to another DNS server, rather than forwarding the query to the root DNS servers. This can be useful in a number of scenarios, such as when you want to improve DNS performance, reduce network traffic, or provide access to DNS servers outside your organization.
There are two types of DNS forwarders: conditional forwarders and stub zones.
- Conditional Forwarders: A conditional forwarder is a type of DNS forwarder that is used to forward queries for a specific domain or set of domains to a specific DNS server. The forwarding can be either conditional or non-conditional. With a non-conditional forwarder, all queries for the specified domains are forwarded to the target DNS server. With a conditional forwarder, the forwarding is based on specific criteria, such as the domain name or IP address of the client making the request.
Function: The primary function of conditional forwarders is to speed up DNS resolution and reduce network traffic by directing queries to a specific DNS server that is authoritative for the domain being queried. This can also provide better control over DNS resolution and security.
Query Flow: When a client sends a DNS query, the DNS server first checks its cache for a matching record. If the record is not found in the cache, the server checks its forwarder configuration to see if there is a conditional forwarder for the requested domain. If there is a matching forwarder, the server sends the query to the specified DNS server, which will then either provide the answer or forward the query to other DNS servers as necessary.
- Stub Zones: A stub zone is a read-only copy of a DNS zone that contains only the necessary records for name resolution. This type of zone is used to forward queries for a specific domain or set of domains to a specific DNS server that is authoritative for the domain being queried.
Function: The primary function of stub zones is to improve DNS performance by reducing the time it takes to resolve queries. This is accomplished by providing a local copy of the necessary records for the queried domain, rather than relying on remote DNS servers to provide the information.
Query Flow: When a client sends a DNS query, the DNS server first checks its cache for a matching record. If the record is not found in the cache, the server checks its stub zone configuration to see if there is a matching zone for the requested domain. If there is a matching zone, the server sends the query to the specified DNS server, which will then either provide the answer or forward the query to other DNS servers as necessary.
DNS forwarders are used to redirect DNS queries for a specific domain or set of domains to another DNS server, rather than forwarding the query to the root DNS servers. There are two types of DNS forwarders: conditional forwarders and stub zones. Conditional forwarders are used to forward queries for a specific domain or set of domains to a specific DNS server based on specific criteria, while stub zones are used to provide a local copy of the necessary records for a queried domain to improve DNS performance.
