Zones and DNS server roles
A zone is a storage database for either a DNS domain or for a DNS domain and one or more of its subdomains. On all Windows 2000 DNS servers except Active Directory-integrated DNS servers, all DNS entries for a zone are contained in single text file called a zone file. On Active Directory-integrated DNS servers. DNS entries are stored in the Active Directory data store instead of in a zone file.
Types of roles performed by DNS server
· Standard primary : This type of DNS server stores DNS entries in a zone file that is maintained on this server. There can only be one standard primary server for zone.
· Active Directory-integrated (Primary) : This type of DNS server is just like a standard prmary server, except that it stores DNS entries in the AD data store, rather in a zone file. Because, AD supports Multiple master replication, There can be more than one AD-integrated DNS server for a zone. Changes can be made on any AD-integrated DNS server that contains the zone.
· Standard secondary : Store copies of zones that it obtains from the standard primary, AD-integrated or another standard secondary DNS server. The process of copying a zone to a standard secondary DNS server is called a Zone transfer.
· Master : This type of DNS server provides a copy of the zone to a standard secondary DNS server. The secondary DNS server receiving the copy of the zone is sometimes called the salve in this relationship.
· Caching-only : This type of DNS server does not store any zones. It resolves host names to IP addresses for client computers, stores the resulting mapping information in its cache. If we configure DNS server to use root server, the DNS server is, by default, a caching–only server.
· Forwarder : This type of DNS server is designated to perform host name resolution for other DNS servers on a company’s internal network when the host name to be resolved resides in a external DNS domain. The forwarder resolved the host name resolution request, caches the results, and returns the mapping information to the internal DNS server that requested it.
· Root server: This type of DNS server contains a copy of a zone for the root domain – either the root domain for the internet, or the root domain for company’s private, internal network. he purpose of the root server is to enable other DNS servers, on a network to access second-level domains on the internet, or to access other second-level domains on the internal network. A root server should be used only when a network is not connected to the internet, or when a network is connected to the internet by using a proxy server. Root hints cannot be configured on Windows 2000 DNS server that is root server
A forward lookup zone is a zone that contains the host name to IP address mappings and information about available services for either a DNS domain or a DNS domain and one or more of its subdomains. A reverse lookup zone is a zone that contains IP address to host name mappings. Reverse lookup zones use WINS-R option. The WINS-R is used to configured the DNS server to use a specified WINS server to resolve IP addresses that the DNS server is unable to resolve by searching the resource records in this zone. DNS server used a forward lookup zone when a client computer know the host name, but doesn’t know the associated IP address. A DNS server uses a reverse lookup zone when a client computer knows the IP address, but doesn’t know the associated host name.
The term recursion refers to repeating a process until a solution is found. By default, recursion is enabled on DNS servers. fThis means DNS server will contact as many other DNS servers as necessary, one after another, to resolve a client DNS query.
BIND secondaries : This option, which is selected by default, causes zones to be transferred from master DNS servers to a secondary DNS server by using fast zone transfer format.
Round robin : This feature is used when multiple servers have identical configurations and identical host names, but different IP addresses. The DNS server, when it contains multiple mappings for the same host name, cycles through its list to provide a different IP address to the requesting client each time the host is requested, thereby providing load balancing for the requested servers.
The three name checking methods that DNS server use are:
· Strict RFC (ANSI)
· Non-RFC (ANSI) and
· Mutibyte (UTF8) is the default setting and permits the DNS server to recognize more characters than either of the other two options.
DNS server will look for its initialization information from one of the following three optins :
· From registry
· From file and
· Active Directory and Registry is a default setting.
Scavenging is the process of searching for and deleting stale resource records. The default scavenging period is seven days.
Five types zones are Forward lookup zone, reverse lookup zone, Standard primary zone, AD-integrated zone and Standard secondary zone.
To Troubleshoot DNS , we can use Monitoring Tab and Nslookup.exe
Troubleshoot DNS issues and Nslookup Advance Usage
Two types of queries used to test the DNS server are
· Simple query is query that this DNS server can resolve without contacting any other DNS servers.
· Recursive query is a query that this DNS cant resolve by itself. It must contact one or more additional DNS servers to resolve the query.