Learning and basics of Microsoft Infra Admins

This blog list the basic questions and answers we come across as System Admins on Microsoft Technologies.

The posts are divided into levels as L1, L2 and L3.



Types of Registry Keys

HKEY_CLASSES_ROOT  : – data on DLL files and applications is stored.

HKEY_CURRENT_USER  –  current user’s individual customizations are stored and tracked.

HKEY_LOCAL_MACHINE: – all of the software installed on the computer. Virtually anything that the operating system might need to know about a particular application is stored here.

HKEY_USERS: – all user data is stored. If multiple people use the same computer, all their user profiles are stored here. When a user logs on to the computer, the data is written to HKEY_CURRENT_USER.

HKEY_CURRENT_CONFIG –  This key points to the current computer hardware configuration in the collection of configurations stored in HKEY_LOCAL_MACHINE. This enables the use of multiple computer hardware profiles.

What are Resource Record Types?


A (host) Contains name-to-IP address mapping information, which is used to map a DNS domain name to a host IP address on the network. An A resource record is also referred to as a host record.NS (name server) Designates the DNS domain names for the servers that are authoritative for a certain zone or that contain the zone file for that domain.

CNAME (canonical name) Allows you to provide additional names to a server that already has a name in an A resource record. For example, if the server called webserver1.nwtraders.msft hosts the Web site for nwtraders.msft, this server must have the common name http://www.nwtraders.msft. A CNAME resource record is also referred to as an alias record.

MX (mail exchanger) Specifies the server to which e-mail applications can deliver mail. For example, if you have a mail server running on a computer named mail1.nwtraders.msft and you want all mail for user_name@nwtraders.msft to be delivered to this mail server, the MX resource record must exist in the zone for nwtraders.msft and must point to the mail server for that domain.

SOA (start of authority) Indicates the starting point or original point of authority for information stored in a zone. The SOA resource record is the first resource record created when you add a new zone. It also contains several parameters used by other computers that use DNS to determine how long they will use information for the zone and how often updates are required.

PTR (pointer) Used in a reverse lookup zone created in the in-addr.arpa domain to designate a reverse mapping of a host IP address to a host DNS domain name.

SRV (service) Registered by services so that clients can locate a service by using DNS. SRV records are used to identify services in Active Directory and are also referred to as Service Location records.

NS Resource Records

The name server (NS) resource record indicates the servers authoritative for the zone. They indicate primary and secondary servers for the zone specified in the SOA resource record, and they indicate the servers for any delegated zones. Every zone must contain at least one NS record at the zone root.



What are the types of DNS Zones?

Standard Primary zone: Contains a local copy of the DNS zone where resource records are created and updated.

Secondary zone: Contains a read-only version of the zone file that is stored in a standard text file. Any changes to the zone are recorded in the primary zone file and replicated to the secondary zone file. Create a standard secondary zone to create a copy of an existing zone and its zone file. This allows the name resolution workload to be distributed among multiple DNS servers.

Active Directory integrated zone: Stores the zone information in Active Directory, rather than a text file. Updates to the zone occur automatically during Active Directory replication. Create an Active Directory integrated zone to simplify planning and configuration of a DNS namespace. You do not need to configure DNS servers to specify how and when updates occur, because Active Directory maintains zone information.

Stub zone: A copy of a zone that contains only the resource records needed to identify authoritative DNS servers, thereby simplifying DNS administration and improving name resolution.                                                                                                                                                     uses its local DNS cache information to resolve DNS queries for clients.

Stub zones contain only:

  • Start of Authority (SOA) record
  • Name Server (NS) records
  • (A) records


What are the DNS Query Types?

Iterative –  query made from a client to a DNS server in which the server returns the best answer that it can provide based on its cache or zone data.

If the queried server does not have an exact match for the request, it provides a pointer to an authoritative server in another level of the domain namespace.

Recursive – query made from a client to a DNS server in which the server assumes the full workload and responsibility for providing a complete answer to the query. The server will then perform separate iterative queries to other servers (on behalf of the client) to assist in answering the recursive query.

By default recursive query is enabled but it can be disabled if you don’t want to use it in your environment.


How GPOs Are Applied (order)


  1.  Local GPO Each server running Windows Server 2003 has exactly one GPO stored locally.
  2. GPOs linked to sites Any GPOs that have been linked to the site are applied next. GPO application is synchronous; the administrator specifies the order of GPOs linked to a site.
  3. GPOs linked to domains Multiple domain-linked GPOs are applied synchronously; the administrator specifies the order of GPOs linked to a domain.
  4. GPOs linked to OUs GPOs linked to the OU highest in the Active Directory hierarchy are applied first, followed by GPOs linked to its child OU, and so on. Finally, the GPOs linked to the OU that contains the user or computer are applied. At the level of each OU in the Active Directory hierarchy, one, many, or no GPOs can be linked. If several group policies are linked to an OU, then they are applied synchronously in an order specified by the administrator.