DNS

DNS provides for domain name to IP address resolution. Host names are not case sensitive and can contain alphabetic or numeric letters or the hyphen. Avoid the underscore. A fully qualified domain name (FQDN) consists of the host name plus domain name as in the following example: computername.domain.com Top level domains are .com, .edu, .net, .org, and more. Second level domains may contain other domains and hosts. DNS Files CACHE.DNS - The DNS Cache file. This file is used to resolve internet DNS queries. It is located in the WINNTROOT\system32\DNS directory and is used to configure a DNS server to use a DNS server on the internet to resolve names not in the local domain. DNS and WINS For the system to use WINS if DNS resolution cannot supply the IP address for a name, all DNS servers must be configured to use WINS. It cannot be done with just the primary DNS server. Types of DNS Servers Three types of name servers: Primary - Locally stored files exist on the name server data base. Secondary - Gets data called a zone transfer from another server that is the zone authority. Caching - Only caches name server information and does not contain its own files. The caching only name server generates no zone transfer traffic. A DNS Server that can communicate outside of the private network to resolve a DNS name query is referred to as forwarder. DNS Queries Recursive - When performed for a client, the DNS server stays with the query until it is resolved. The answer is returned or an error is returned. Iterative - The server when it does not have the answer will refer the client to another name server that may have the answer. The best answer the name server has is returned even if it is partial. Usually used between name servers to obtain partial name resolutions. Reverse - The client provides the IP address and asks for the name. In other queries the name is provided, and the IP address is returned to the client. Reverse lookup entries for a network 192.168.100.0 is "100.168.192.in-addr arpa".

WINS Reverse Lookup

A WINS-R record at the root zone of DNS allows WINS to be used by DNS for reverse lookup. WINS reverse lookup is enabled at the "WINS Reverse Lookup" property page by doing the following:

• Check the "Use WINS Reverse Lookup" checkbox.
• Enter the DNS Host Domain to be added to the NetBIOS name.

WINS TTL

The "WINS Lookup" property page (in DNS?) is used to set the WINS TTL(Time to Live) for returned queries.

DNS Record Types

• A - Address record allowing a computer name to be translated into an IP address. Each computer must have this record for its IP address to be located. These names are not assigned for clients that have dynamically assigned IP addresses, but are a must for locating servers with static IP addresses.
• CNAME - Canonical name allowing additional names or aliases to be used to locate a computer.
• HINFO - Host information record with CPU type and operating system.
• MX - Mail Exchange server record. There may be several.
• NS - Name server record. There may be several.
• RP - Responsible person.

DNS Transport protocol

DNS resolvers first attempt to use UDP for transport, then use TCP if UDP fails.