Top 77 Interview Questions for IT Professionals

1. What is the difference between a hub and a switch? HUB works on Physical layer where as SWITCH works on data link layer, HUB based networks are on one collision domain where as in Switch based network switch divides networks into multiple collision domains. Switch also maintains MAC address tables. 2. What is a network? A computer network, often simply referred to as a network, is a collection of computers and devices interconnected by communications channels that facilitate communications among users and allows users to share resources. 3. What is Active Directory? An active directory is a service that is provided by Microsoft that stores information about items on a network so the information can be easily made available to specific users through a logon process and network administrators. By using an Active Directory it is possible to view an entire series of network objects from a single point and obtain an overall hierarchal view of the network. 4. What is TCP/IP and what does it stand for? TCP/IP stands for Transmission Control Protocol / Internet Protocol - the set of rules for communicating There are several sub-protocols within TCP/IP: 1. Internet Protocol (IP), which covers fundamentals like IP addresses and routing of packets of data from one place to another, but doesn't address issues like reliability and delivery in the correct order. 2. Transmission Control Protocol (TCP), which adds the idea of a reliable connection that always delivers a stream of data in the correct order. 5. What is a default gateway? In computer networking, a default gateway is the device that passes traffic from the local subnet to devices on other subnets. The default gateway often connects a local network to the Internet. 6. What does DHCP stand for? DHCP stands for Dynamic Host Configuration Protocol and it is used by networked devices (clients) to obtain automatically various parameters necessary for the clients to operate in an IP network like IP address, default gateway, subnet mask and DNS server(s). 7. What is an IP Address? An identifier for a computer or device on a TCP/IP network. Networks using the TCP/IP protocol route messages based on the IP address of the destination. The format of an IP address is a 32-bit numeric address written as four numbers separated by periods. Each number can be zero to 255. For example, 1.160.10.240 could be an IP address. Arbab Nazar [email protected]

8. What is the significance of the IP address 255.255.255.255? The limited broadcast address is utilized when an IP node must perform a one-to-everyone delivery on the local network but the network ID is unknown. 9. What are the 3 major classes of an IP network? There 3 major classes of IP Network, i.e. Class A, B & C. In details are as follows, Class A 0 0.0.0.0 126.255.255.255 /8 Class B 10 128.0.0.0 191.255.255.255 /16 Class C 110 192.0.0.0 223.255.255.255 /24 10. What is a Class D IP address? Class D range from 224.0.0.0 to 239.255.255.255 and is exclusively reserved for multicast groups. Multicast is a packet transmission technique by which the packets or messages are sent across a network by a single host to a multiple clients or devices. 11. What is OSPF? OSPF is a link state routing protocol that updates the routing table only when network changes occur, rather than at a predefined interval. OSPF supports variable length subnet masks (VLSM) and route summarization.

12. A user is complaining of delays when using the network. What would you do? There are lot of concerns that cause network delays, The Administrator / Network Engineer must check the following simple tasks before he / she proceed. • Get the user(s) to demonstrate the problem. • Determine how many other users are affected. • Ensure desktop hardware and configuration is OK. • Trace all connections (they may be on another subnet). • Commence some monitoring or diagnostics. • Check that the switch port is set to full duplex • That the computer's network drivers are up to date • determining problem (if there is one). • Check for the virus / spyware activity. • If everything seems OK, then try to restart the router / switch, same time try to restart the system. Network Administrator Positions 13. What is the difference between layer 2 and layer 3 in the OSI model? Layer 2(Datalink Layer) is responsible for sending data b/w 2 node (within MAC resolution) and Flow, sequence control and error recovery by retransmission). While layer 3 (Network Layer) is transport the container

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of data with inter network. it needs service of 3,4,5 layer to established session,authentication,packaging data,identification of data.

14. What is the difference between a hub, switch, and router? A Hub is, in its simplest form, just like a mains multiplug unit. There is no intelligence or circuitry in it. More complex units may incorporate an amplifier or repeater. The network signal goes into one port and out of all the others. This is a Layer 1 device. A Switch has a small level of intelligence, in that it can open a message, check the IP address, and direct the message packets to the port on which the device with that IP address resides. It cannot modify IP addresses or see addresses outside of the range of the 'home' network. This is a Layer 2 device. A Router can read IP addresses, and direct the messages to another network with different IP addresses to the originating network. The Router software can build up an address table, so that it 'knows' where other devices are. This is a Layer 3 device. 15. What is a VLAN? Virtual Local Area Network (VLAN) may be defined as a group of LANs that have different physical connections, but which communicate as if they are connected on a single network segment. VLANs were created because it increases overall network performance by grouping users and resources that communicate most frequently with each other. This means that the use of unicast or broadcast data transmission is limited, and traffic is reduced. 16. What is the difference between TCP and UDP? TCP is a Transmission Control Protocol and UDP is a User Datagram Protocol. There are four major differences between UDP and TCP: 1. TCP can establishes a Connection and UDP cannot. 2. TCP provides a stream of unlimited length, UDP sends small packets. 3. TCP gurantees that as long as you have a connection data sent will arrive at the destination, UDP provides not guarantee delivery. 4.UDP is faster for sending small amounts of data since no connection setup is required, the data can be sent in less time then it takes for TCP to establish a connection. 17. How do you distinguish a DNS problem from a network problem? If you are able to ping to a router or switch connected to DNS server but not able to ping DNS server. This is surely a problem with DNS....else its problem in the network. We can also use nslookup tool as well. 18. What are a runt, Giant, and Late collision?

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A runt is a packet that fails to meet the minimum size standard. Usually below 64 bytes. Occurs as a result of a collision. A giant is a packet that exceeds the size standard for the medium usually grater then 1518 bytes . Caused by malfunctioning equipment on your network. Late collisions are packet collisions that occur after the window for a network collision closes. 19. What is a broadcast storm? A state in which a message that has been broadcast across a network results in even more responses, and each response results in still more responses in a snowball effect. A severe broadcast storm can block all other network traffic, resulting in a network meltdown. Broadcast storms can usually be prevented by carefully configuring a network to block illegal broadcast messages. 20. What is the purpose of VRRP? Virtual Router Redundancy Protocol (VRRP) is a non- proprietary redundancy protocol and it is used to avoid single point of failure of a gateway. 21. What is a VPN? A Virtual Private Network (VPN) is a network technology that creates a secure network connection over a public network such as the Internet or a private network owned by a service provider.

22. What is a default route? Default route is configured during the network configuration when the traffic comes to that network having no defined destination or route then that is sent on the default route.

23. How do you set a default route on an IOS Cisco router? configure terminal ip route 0.0.0.0 0.0.0.0 s0/0 The ip route quad zero command will make anything that the router cannot find a route for go out the serial 0/0 interface. 24. What is a metric? Metrics is a property of a route in computer networking, consisting of any value used by routing algorithms to determine whether one route should perform better than another. 25. What is a MAC address? A MAC address, or Media Access Control address, is a 48- or 64-bit address associated with a network adapter. While IP addresses are associated with software, MAC addresses are linked to the hardware of

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network adapters. For this reason, the MAC address is sometimes called the hardware address, the burned-in address (BIA), or the physical address. 26. What is ARP/RARP? ARP (Address Resolution Protocol) - The protocol that traces IP addresses to MAC addresses. RARP (Reverse Address Resolution Protocol) - The protocol within the TCP/IP stack that maps MAC addresses to IP addresses. 27. Describe a TCP connection sequence. The connection establishment process actually accomplishes several things as it creates a connection suitable for data exchange: o Contact and Communication: The client and server make contact with each other and establish communication by sending each other messages. The server usually doesn’t even know what client it will be talking to before this point, so it discovers this during connection establishment. O Sequence Number Synchronization: Each device lets the other know what initial sequence number it wants to use for its first transmission. O Parameter Exchange: Certain parameters that control the operation of the TCP connection are exchanged by the two devices. 28. What is MTU? Short for Maximum Transmission Unit, the largest physical packet size, measured in bytes that a network can transmit. Any messages larger than the MTU are divided into smaller packets before being sent. 29. What other TCP setting can you modify besides MTU to shorten packets? Shorten the byte using ping command -l option System Administration Position 30. What is the difference between layer 2 and layer 3 devices? L-2 devices worked on mac address & L-3 devices worked on ip address. L-2 device faster than the L-3 device. 31. What is the subnet for a class C network? For class c Network default Subnet mask is 255.255.255.0 but make sure while putting a question its subnet or subnet mask.

32. Have you configured a NIS server/client before? If so, describe what you did. I don’t know Linux……so kindly someone else answer this question please

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33. Have your configured a NFS server? There are three ways to configure an NFS server under Red Hat Enterprise Linux: using the NFS Server Configuration Tool (redhat-config-nfs), manually editing its configuration file (/etc/exports), or using the /usr/sbin/exportfs command.

34. What are RAID 1 and RAID 5?

Following are the key points to remember for RAID level 1. • • •

Minimum 2 disks. Good performance ( no striping. no parity ). Excellent redundancy ( as blocks are mirrored ).

Following are the key points to remember for RAID level 5. • • • •

Minimum 3 disks. Good performance ( as blocks are striped ). Good redundancy ( distributed parity ). Best cost effective option providing both performance and redundancy. Use this for DB that is heavily read oriented. Write operations will be slow.

35. What are the required components of Windows Server 2003 for installing Exchange 2003? Prior to installing Exchange server 2003 , following Windows component must be installed. 1>Active Directory & DNS 2> Microsoft.net framework 3> MicrosoftASP.net 4> World Wide Web services (WWW ) 5> Simple mail transfer protocol (SMTP ) 6> Network New TRansfer Protocol ( NNTP )

36. What must be done to an AD forest before Exchange can be deployed? First run forestprp

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then domain prep then Setup.exe 37. What Exchange process is responsible for communication with AD? DSACCESS- Directory service access (dsa.msc)

38. What connector type would you use to connect to the Internet, and what are the two methods of sending mail over that connector? SMTP Connector: Forward to smart host or use DNS to route to each address 39. How would you optimize Exchange 2003 memory usage on Windows Server 2003 with more than 1Gb of memory? If you have over 1GB of RAM on the server, it's also important that you set the /3GB switch in the Boot.ini file. This tells Exchange to use a different and more efficient method for assigning memory to file handles (a data structure called a PTE.) 40. What are the standard port numbers for SMTP, POP3, IMAP4, RPC, LDAP and Global Catalog? SMTP-25, POP3-110, IMAP4-143, RPC-135, LDAP-389, GC-3268 41. Name the process names for the following: System Attendant, Information Store, SMTP/POP/IMAP/ OWA. MAD.EXE, Information Store – STORE.EXE, SMTP/POP/IMAP/OWA -INETINFO.EXE 42. What is the maximum amount of databases that can be hosted on Exchange 2003 Enterprise? 20 databases. 4 SGs x 5 DBs. 43. What are the disadvantages of circular logging? In the event of a corrupt database, data can only be restored to the last backup. 44. What is Active Directory schema? The Microsoft Active Directory schema contains formal definitions of every object class that can be created in an Active Directory forest. The schema also contains formal definitions of every attribute that can exist in an Active Directory object. 45. What are the domain functional levels in Windows Server 2003?

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The domain functional levels are the various states of a domain, which enable domain-wide Active Directory features within a network environment. Domain levels are the same as domain modes in Windows 2000. Windows supports four types of functional levels: 1. Windows 2000 Mixed: This is the default domain functional level. When a first domain controller is installed or upgraded to Windows 2003, the domain controller is configured to run in the Windows 2000 mixed functional level. In this mode, domain controllers running the following operating systems are supported: o Windows NT Server 4.0 o Windows 2000 Server o Windows Server 2003 2. Windows 2000 Native: In this level, domain controllers running Windows 2000 and Windows 2003 can interact with each other. No domain controller running a pre-Windows 2000 version is supported in this functional level of the domain. 3. Windows Server 2003 Interim: This functional level allows a Windows Server 2003 domain controller to interact with domain controllers in the domain running Windows NT 4.0 or Windows Server 2003. This functional level is used to upgrade the first Windows NT domain to a new forest. Note: Windows Server 2003 interim functional level does not support domain controllers running Windows 2000. 4. Windows Server 2003: This functional level of domain allows a Windows Server 2003 domain controller to interact only with the domain controllers running Windows 2003 in the domain. A domain level can be raised to Windows Server 2003 only when all the domain controllers in the domain are running Windows Server 2003. Note: Once a domain functional level is raised, it cannot be changed. 46. What is the default domain functional level in Windows Server 2003? Windows 2000 Mixed: This is the default domain functional level. 47. What are the forest functional levels in Windows Server 2003? Forest functionality activates features across all the domains in your forest. Three forest functional levels, the corresponding features, and their supported domain controllers are listed below. Windows 2000 (default) Windows Server 2003 interim Windows Server 2003 48. What is a global catalog server? A global catalog server is a domain controller that stores a full copy of all objects in the directory for its host domain and a partial, read-only copy of all objects for all other domains in the forest. Global catalog servers respond to global catalog queries.

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49. How can we raise domain functional and forest functional levels in Windows Server 2003?

50. What is the default protocol used in directory services? NTLM, LDAP, SMTP & RPC protocol 51. What is IPv6? IPv6 (Internet Protocol version 6) is similar to those of IPv4 -- devices can use IPv6 as source and destination addresses to pass packets over a network. The most obvious improvement in IPv6 over IPv4 is that IP addresses are lengthened from 32 bits to 128 bits. IPv6 also supports auto-configuration to help correct most of the shortcomings in version 4, and it has integrated security and mobility. 52. What are the physical & logical components of ADS? The logical structure consists of OUs, domains, trees, and forests. The logical structure helps you design a network hierarchy that suits your organizational needs. The physical structure consists of sites and domain controllers. The physical structure helps you optimize network traffic by customizing the network configuration. 53. In which domain functional level, we can rename a domain name? Forest and Domain functional levels must be Windows 2003 Native

54. What is multimaster replication? Active Directory uses multimaster replication to accomplish the synchronization of directory information. True multimaster replication can be contrasted with other directory services that use a master-slave approach to updates wherein all updates must be made to the master copy of the directory and then be replicated to the slave copies. 55. What is a site? Arbab Nazar [email protected]

Active Directory (AD) sites, which consist of well-connected networks defined by IP subnets that help define the physical structure of your AD, give you much better control over replication traffic and authentication traffic. 56. Which is the command used to remove active directory from a domain controller? You use the same command you used to make a server a domain controller, DCPROMO. Now, before you remove Active Directory from a server, you need to transfer any FSMO roles that it might have, assuming you are keeping the rest of active directory. If this is the only domain controller, and the existing active directory is just going to go away, then just run DCPROMO and follow the prompts. 57. What is the file that’s responsible for keeping all Active Directory databases? The Active Directory Database is Stored in %SYSTEM ROOT%\NDTS folder. The file is called as ntds.dit. Along with this file there are other files also present in this folder. 1. 2. 3. 4. 5.

ntds.dit edb.log res1.log res2.log edb.chk

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