DNS Authoritative Server

AE.

An authoritative server is a DNS server that is considered the final authority for a particular domain name. It is responsible for providing authoritative answers to DNS queries for the domain or zone it is authoritative for. Here are the statements that are true about authoritative servers:

A. It indicates that it is authoritative for a name by setting the AA bit in responses. This statement is true. The AA (Authoritative Answer) bit is set in a DNS response when the responding DNS server is authoritative for the queried domain name. This bit indicates to the requesting DNS resolver that the response can be trusted and does not need to be further resolved by other DNS servers.

B. It has a direct connection to one of the root name servers. This statement is not necessarily true. While it is true that the root name servers are authoritative for the top-level domain names, authoritative servers for other domain names may not have a direct connection to any root name server. Instead, they may be connected to other authoritative servers or to DNS resolvers that can provide them with the necessary information to respond to DNS queries.

C. It has a ratio of exactly one authoritative name server per domain. This statement is not true. While it is recommended to have at least two authoritative name servers for redundancy and fault tolerance, there is no fixed ratio of authoritative name servers per domain. The number of authoritative name servers required depends on the size and importance of the domain.

D. It cannot cache or respond to queries from domains outside its authority. This statement is not true. While an authoritative server is responsible for providing authoritative answers only for the domain or zone it is authoritative for, it can still cache DNS information and respond to queries from other domains. However, it will not provide authoritative answers for those queries.

E. It has a ratio of at least one authoritative name server per domain. This statement is generally true. It is recommended to have at least two authoritative name servers for a domain for redundancy and fault tolerance. Having only one authoritative name server can make the domain vulnerable to DNS outages and attacks. However, some small domains may be served by a single authoritative name server without causing significant issues.