What is active directory


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What is active directory

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What is active directory

  1. 1. Server Related Interview Question and Answer Server Active Directory What is Active Directory? Active directory is a hierarchical structure that stores information about objects on the network. Active Directory provides the methods for storing directory data and making this data available to network users and administrators. Active Directory Default Storage? Active Directory Data base folder: - D:WINDOWSNTDS Store active Directory log: - D:WINDOWSNTDS SYSVOL:-The SYSVOL folder stores the server copy of domain public files. The contents of the SYSVOL folder are replicated to all domain controllers in the domain. Its must be located on an NTFS Volume SYSVOL By default Location: - D:WINDOWSSYSVOL What is Domain? In Active Directory, a collection of computer, user, and group objects defined by the administrator. These objects share a common directory database, security policies, and security relationships with other domains. In Domain Name System (DNS), a domain is any tree or sub tree within the DNS namespace. Although the names for DNS domains often correspond to Active Directory domains, DNS domains should not be confused with Active Directory domains. What is Domain Controller? In an Active Directory forest, a server that contains a writable copy of the Active Directory database participates in Active Directory replication, and controls access to network resources. Administrators can manage user accounts, network access, shared resources, site topology, and other directory objects from any domain controller in the forest. See also Active Directory; authentication; directory; forest. What is Domain Services? Active Directory provides the means to manage the identities and relationships that make up your organization's network. Integrated with Windows Server 2008, Active Directory gives you out-of-the-box functionality needed to centrally configure and administer system, user, and application settings. Active Directory Domain Services (AD DS) stores directory data and manages communication between users and domains, including user logon processes, authentication, and directory searches. What is Global Catalog (GC)? A domain controller that contains a partial replica of every domain in Active Directory. A global catalog holds a replica of every object in Active Directory, but with a limited number of each object’s attributes. The global catalog stores those attributes most frequently used in search operations (such as a user’s first and last names) and those attributes required to locate a full replica of the object. The Active Directory replication system builds the global catalog automatically. The attributes replicated into the global catalog include a base set defined by Microsoft. Administrators can specify additional properties to meet the needs of their installation. What is Forest? A collection of one or more Active Directory domains that share a common schema, configuration, and global catalog. 1
  2. 2. Server Related Interview Question and Answer What is tree? A tree in Active Directory is just an extension of the idea of a directory tree. It’s a hierarchy of objects and containers that demonstrates how objects are connected, or the path from one object to another. Endpoints on the tree are usually objects. What is Site? One or more well-connected (highly reliable and fast) Transmission Control Protocol/Internet Protocol (TCP/IP) subnets. A site allows administrators to con-figure Active Directory access and replication topology quickly and easily to take advantage of the physical network. When users log on, Active Directory clients locate Active Directory servers in the same site as the user. See also subnet; well-connected. What is Organizational unit (OU)? A container object in Active Directory used to separate computers, users, and other resources into logical units. An organizational unit is the smallest entity to which Group Policy can be linked. It is also the smallest scope to which administration authority can be delegated. What is Schema? A description of the object classes and attributes stored in Active Directory. For each object class, the schema defines what attributes an object class must have, what additional attributes it may have, and what object class can be its parent. An Active Directory schema can be updated dynamically. For example, an application can extend the schema with new attributes and classes and use the extensions immediately. Schema updates are accomplished by creating or modifying the schema objects stored in Active Directory. Like every object in Active Directory, a schema object has an access control list (ACL) so that only authorized users can alter the schema. Windows DNS 1) What is DNS? The Domain Name System (DNS) is a hierarchical distributed naming system for computers. The Domain Name System distributes the responsibility of assigning domain names and mapping those names to IP addresses by designating authoritative name servers for each domain. Authoritative name servers are assigned to be responsible for their particular domains, and in turn can assign other authoritative name servers for their sub-domains. 2) What is the main purpose of a DNS server? DNS servers are used to resolve FQDN hostnames into IP addresses and vice versa. 3) How does a computer know to which DNS server it has to sent the request The DNS server IP address is configured on the TCP/IP adapter setting of the computer. With this information, the computer knows the DNS server to which the request has to be sent. 4) What is the port no of DNS? UDP port number - 53 5) How many root DNS servers are available in the world? 13 6) What is a Forward Lookup? Resolving Host Names to IP Addresses, Address mapping (A) records maps a host name to an IP address 7) What is a Forward Lookup? Reverse-lookup pointer (PTR) records map an IP address to a host name. 8) What is a Resource Record? It is a record provides the information about the resources available in the N/W infrastructure. 9) What is the different DNS Roles? Standard Primary, Standard Secondary, & AD Integrated. 2
  3. 3. Server Related Interview Question and Answer 10) What is a Zone? Zone is a sub tree of DNS database. 11) Why we create PTR Records Secure services in your network require reverse name resolution to make it more difficult to launch successful attacks against the services. To set this up, you configure a reverse lookup zone and proceed to add records. 12) SOA records must be included in every zone. What are they used for? SOA records contain a TTL value, used by default in all resource records in the zone. SOA records contain the e-mail address of the person who nis responsible for maintaining the zone. SOA records contain the current serial number of the zone, which is used in zone transfers. 13) What is primary, Secondary, stub & AD Integrated Zone? Primary Zone: - zone which is saved as normal text file with filename (.dns) in DBS folder. Holds the master copy of a zone and can replicate it to secondary zones. All changes to a zone are made on the standard primary. Secondary Zone: - maintains a read only copy of zone database on another DNS server. Provides fault tolerance and load balancing by acting as backup server to primary server.Information in a primary zone is replicated to the secondary by use of the zone transfer mechanism. Stub zone: - contains a copy of name server and SOA records used for reducing the DNS search orders. Provides fault tolerance and load balancing. Active Directory-integrated: -A Microsoft proprietary zone type, where the zone information is held in the Windows 2000 Active Directory (AD) and replicated using AD replication. DNS record types 14) What is the main purpose of SRV (Service)records? SRV records are used in locating hosts that provide certain network services. 15) Which of the following conditions must be satisfied to configure dynamic DNS updates for legacy clients? The zone to be used for dynamic updates must be configured to allow dynamic updates. The DHCP server must support, and be configured to allow, dynamic updates for legacy clients. 16) Benefits of using AD-integrated zones. a) Active Directory integrated DNS enables Active Directory storage and replication of DNS zone databases. Windows 2000 DNS server, the DNS server that is included with Windows 2000 Server, accommodates storing zone data in Active Directory. b) When you configure a computer as a DNS server, zones are usually stored as text files on name servers that is, all of the zones required by DNS are stored in a text file on the server computer. c) These text files must be synchronized among DNS name servers by using a system that requires a separate replication topology and schedule called a zone transfer However, if you use Active Directory integrated DNS when you configure a domain controller as a DNS name server, zone data is stored as an Active Directory object and is replicated as part of domain replication. Dynamic Host Configure Protocol – DHCP  DHCP allows to automatically assigning IP addresses, subnet masks, and other configuration information to client computers on the local network. When a DHCP server is available, computers that are configured to obtain an IP address automatically request and receive their IP configuration from that DHCP server upon booting. When a DHCP server is unavailable, such clients automatically adopt an alternate configuration or an Automatic Private IP Addressing (APIPA) address. There are two versions of DHCP, one for IPv4 and one for IPv6. While both versions bear the same name and perform much the same purpose, 3
  4. 4. Server Related Interview Question and Answer      DHCP uses the same two ports assigned by IANA for BOOTP: UDP port 67 for sending data to the server, and UDP port 68 for data to the client. DHCP communications are connectionless in nature. Working Process Normally the DHCP server provides the client with at least this basic information: IP Address Subnet Mask Default Gateway Other information can be provided as well, such as Domain Name Service (DNS) server addresses and Windows Internet Name Service (WINS) server addresses. The system administrator configures the DHCP server with the options that are parsed out to the client. When a client is initialized for the firs t time after it is configured to receive DHCP information, it initiates a conversation with the server. The detailed conversation between DHCP client and DHCP server is as follows: DHCP-Discover The client sends a DHCPDISCOVER packet. The following is an excerpt from a network monitor capture showing the IP and DHCP portions of a DHCPDISCOVER packet. In the IP section, you can see the Destination address is and the Source address is The DHCP section identifies the packet as a Discover packet and identifies the client in two places using the physical address of the network card. Note the values in the CHADDR field and the DHCP: Client Identifier field are identical. DHCP-Offer The DHCP server responds by sending a DHCPOFFER packet. In the IP section of the capture excerpt below, the Source address is now the DHCP server IP address, and the Destination address is the broadcast address The DHCP section identifies the packet as an Offer. The YIADDR field is populated with the IP address the server is offering the client. Note the CHADDR field still contains the physical address of the requesting client. Also, we see in the DHCP Option Field section the various options being sent by the server along with the IP address. In this case the server is sending the Subnet Mask, Default Gateway (Router), Lease Time, WINS server address (NetBIOS Name Service), and the NetBIOS Node Type. DHCP-Request The client responds to the DHCPOFFER by sending a DHCPREQUEST. In the IP section of the capture below, the Source address of the client is still and the Destination for the packet is still The client retains because the client hasn't received verification from the server that it's okay to start using the address offered. The Destination is still broadcast, because more than one DHCP server may have responded and may be holding a reservation for an Offer made to the client. This lets those other DHCP servers know they can release their offered addresses and return them to their available pools. The DHCP section identifies the packet as a Request and verifies the offered address using the DHCP: Requested Address field. The DHCP: Server Identifier field shows the IP address of the DHCP server offering the lease. DHCP-Acknowledgment The DHCP server responds to the DHCP-REQUEST with a DHCP-ACK, thus completing the initialization cycle. The Source address is the DHCP server IP address, and the Destination address is still The YIADDR field contains the client's address, and the CHADDR and DHCP: Client Identifier fields are the physical address of the network card in the requesting client. The DHCP Option section identifies the packet as an ACK. 4
  5. 5. Server Related Interview Question and Answer File Transfer Protocol – FTP FTP - File Transfer Protocol Port Number - 21 OSI Model - Application Layer File Transfer Protocol (FTP) is a standard network protocol used to transfer files from one computer to another over a TCP-based network, such as the Internet or Local Area network. FTP is part of the TCP/IP protocol suite. TCP/IP is the basic protocol that runs the whole Internet. There are a number of smaller protocols that run on top of TCP/IP, such as email, HTTP, and Telnet. FTP is one of these. FTP operates on the application layer of the OSI model, and is used to transfer files using TCP/IP. How does Work FTP works on the principal of a client/server. FTP works very similarly to the way web pages work. Each file on an FTP server is given an address (URL) so that other computers connected to the internet can find it. Users can then either use an FTP client or most web browsers to either download or upload files to the server. When a user wishes to engage in File transfer, FTP sets up a TCP connection to the target system for the exchange of control messages. These allow used ID and password to be transmitted and allow the user to specify the file and file action desired. Once file transfer is approved, a second TCP connection is set up for data transfer.        FTP and TFTP Windows NT supports both file transfer protocol (FTP) and trivial file transfer protocol (TFTP) under its implementation of TCP/IP. Both of these protocols can be used for transferring files across the Internet. The differences between the two protocols are explained below: FTP is a complete, session-oriented, general purpose file transfer protocol. TFTP is used as a bare-bones special purpose file transfer protocol. FTP can be used interactively. TFTP allows only unidirectional transfer of files. FTP depends on TCP, is connection oriented, and provides reliable control. TFTP depends on UDP, requires less overhead, and provides virtually no control. FTP provides user authentication. TFTP does not. FTP uses well-known TCP port numbers: 20 for data and 21 for connection dialog. TFTP uses UDP port number 69 for its file transfer activity. The Windows NT FTP server service does not support TFTP because TFTP does not support authentication. Windows 95 and TCP/IP-32 for Windows for Workgroups do not include a TFTP client program. Passive and active FTP Internet Information Server (IIS) with File Transmission Protocol (FTP) installed supports the following connection types: Active-mode FTP Passive-mode FTP The IIS-based FTP service (MSFTPSVC) supports both active and passive mode connections, depending on the method that is specified by the client. The FTP protocol uses a minimum of two connections during a session: a half-duplex connection for control, and a full-duplex connection for data transfer. By default, TCP port 21 is used on the server for the control connection. Active Mode FTP Connection Active-mode FTP is sometimes referred to as "client-managed" because the client sends a PORT command to the server (over the control connection) that requests the server to establish a data connection from TCP Port 20 on the server, to the client, using the TCP port that is specified by the PORT command. [Note: -The FTP client sends the PORT command to the FTP server in the following format: 5
  6. 6. Server Related Interview Question and Answer PORT 192,168,0,3,19,243 where the first four comma-separated values correspond to the octets of the client's IP address, and the fifth and sixth values are the high- and low-order bits of the 16-bit port number.] Passive-mode FTP Connections Passive-mode FTP is sometimes referred to as "server-managed", because after the client issues a PASV command, the server responds to that PASV instruction with one of its ephemeral ports that will be used as the server-side port of the data connection. After a data connection command is issued by the client, the server connects to the client using the port immediately. Anonymous FTP A host that provides an FTP service may additionally provide anonymous FTP access. Users typically log into the service with an 'anonymous' account when prompted for user name. Although users are commonly asked to send their email address in lieu of a password, no verification is actually performed on the supplied data. Many FTP hosts whose purpose is to provide software updates will provide anonymous logins. Examples of anonymous FTP servers can be found here. Some universities, government agencies, companies, and private individuals have set up public archives that you may access via FTP, usually in a directory named pub for anonymous FTP. Internet Information Service - IIS What is IIS? Internet Information Services (IIS) is a web server application and set of feature extension modules created by Microsoft for use with Microsoft Windows. It is the most used web server after Apache HTTP Server. Latest edition is IIS-7.5 it supports HTTP, HTTPS, FTP, FTPS, SMTP and NNTP. It is an integral part of Windows Server family of products, as well as certain editions of Windows XP, Windows Vista and Windows 7. IIS is not turned on by default when Windows is installed. 6