Configuring DNS Server Part1

Configure DNS in Server 2008 Part1

DNS resolves host names to IP addresses and can also resolve IP addresses to host names in reverse order. Name resolution is important for IP address because IP addresses are difficult to remember and we mostly use host names or fully qualified domain names (FQDNs) for example, in Internet addresses such as www.dixitmicro.com.

Types of name resolution methods that are used to resolve hostnames:

Hosts File.
This is a text file that you can use to enter hostnames and IP addresses. it is located in the C:\Windows\System32\Drivers\etc folder.

Host cache.
When a name is resolved from DNS, it is automatically placed in the host cache. Additionally, You can view the host cache using the ipconfig /DisplayDNS command.

Link-Local Multicast Name Resolution (LLMNR).
LLMNR is new and is supported on Windows Vista, Windows Server 2008 and later Operating systems. LLMNR is sometimes referred to as multicast DNS (mDNS) and is used to resolve names on a local network segment when a DNS server is not available.

DNS GNZ.
DNS servers in Windows Server 2008 can host a GlobalNamesZone that is used for single-label name (GlobalNames) resolution. This works similarly to how NetBIOS names are resolved by a WINS name server. The difference between WINS and GNZ is that WINS uses NetBIOS names that can be max. 16 charecters but GNZ uses GlobalNames (flat name) that can be more than 16 charecter but can not resolve FQDN as done by DNS.

Types of Names used in name resolution process.

A- Hostname
Hostnames are used to identify system on the network. A hostname can have as many as 256 characters.

B- NetBIOS names
NetBIOS names are used only within internal networks and are used to identify systems within the network. A NetBIOS name is composed of 16 characters, but only the first 15 characters are readable. The last character identifies the service running on the computer.

C- Global Names
The addition of GlobalNamesZone and global names is intended to assist enterprises in eliminating the use of WINS in the network.

Usefull commands
 nbtstat -c                          Display netbios cache entry
 ipconfig /displaydns         Display host cache
 ipconfig /flushdns             Remove host cache.

ZONE
When discussing DNS, we use the term zones. In DNS zone is a group of resource records associated with a specific namespace used to mapping IPaddress  to hostname, hostname to IPaddress, name to service and more. Zones are divided into zone types, zone files, and zone records.


Zone types 
The following are the zone types:

1- Primary Zone:    Store read and write copy of all records.
2- Secondary Zone:   Read only copy of primry zone to provide loadbalancing for DNS servers.
3- Stub Zone:      Does not store all records, instead of full records it store the records(A, SOA, NS) that is needed to communicate with authoritative DNS.

4- Active Directory–integrated:  Zone that store information in active directory (usually in domain network).

5- Statndard Zone:   Zone that store information in plain text file (usually in workgroup network).
4- GlobalNamesZone:
To understand GNZ better, remember that hostnames are traditionally resolved using the
fully qualified domain name (such as dixitmicro.blogspot.com) by DNS and that NetBIOS names
are typically resolved using a single label or flat namespace (such as only dixitmicro) by
WINS. When using a GNZ, DNS is able to resolve names using the single label name.

Before a GlobalNameszone can be created, you must enable it. use this command to enable GNZ Zone
Dnscmd ServerName /config /EnableGlobalNamesSupport 1

NOTE:  Authoritative DNS
If a DNS server is responsible for maintaining records for a given namespace, it is considered authoritative for that zone.

Zone files
The following are the zone files:
A- Forward lookup zone file (holds A records, and more). This is used to provides hostname to IP address resolution using host records.

B- Reverse lookup zone file (holds Pointer (PTR) records). This provides IP address to hostname
resolution.

Zone resource records 
The following are the zone resource records:

Host: The A, or host record, maps a hostname to an IPv4 address. This is the  most common type of record in DNS. (A) IPv4, AAAA (IPv6).

PTR: It provides mapping from the IP address to a name. 

SOA: SOA The start of authority (SOA) record provides a lot of key information on the DNS server like as Serial number, responsible person, refresh interval, Expiry time etc. IT is automatically created when DNS is installed.

 SRV: SRV records are used to identify servers running specific services within the domain.
  
 NS: The NS record is used to identify DNS name servers.

 MX: Mail exchanger (MX) records are used to identify mail servers.

 CNAME: (alias) A CNAME record is used to allow a single server to respond to multiple nickname or shortname.

DNS dynamic update (DDNS)
The dynamic update feature allows the A and PTR records within DNS to be created automatically

Dynamic update is configured in three locations:
1- DNS settings for dynamic update In the General properties tab of a DNS zone,

2- DHCP settings for dynamic update The DHCP server is configured by default to use dynamic updates.

3- Client settings for dynamic update The client settings for dynamic update can be configured in the LAN properties.