DHCP Interview Questions & Answers

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DHCP Interview Questions & Answers

Are you in search of DHCP jobs? Then we have provided a complete set of interview questions and answers on our site page to clear the interview in the first attempt. We have also provided the various job roles in the DHCP on our site page. To be precise DHCP means Dynamic Host Configuration Protocol (DHCP) is a network management protocol used on TCP/IP networks. If you are good at the DHCP concepts then there are various leading companies that offer jobs in various roles like Infrastructure Developer - Python DNS/DHCP/IP Automation, Active Directory Administrator L3, Tech Specialist - Windows/Active Directory Administration, Senior Engineer/ Technical Specialist and many other roles too. To know more on DHCP Jobs and DHCP interview question and answers visit our site www.wisdomjobs.com.

DHCP Interview Questions

DHCP Interview Questions
    1. Question 1. What Is Dhcp?

      Answer :

      Dynamic Host Configuration Protocol (DHCP) is a network protocol that enables a server to automatically assign an IP address to a computer from a defined range of numbers (i.e., a scope) configured for a given network.

    2. Question 2. What Is The Dhcp Process For Client Machine?

      Answer :

      1. A user turns on a computer with a DHCP client.
      2. The client computer sends a broadcast request (called a DISCOVER or DHCPDISCOVER), looking for a DHCP server to answer.
      3. The router directs the DISCOVER packet to the correct DHCP server.
      4. The server receives the DISCOVER packet. Based on availability and usage policies set on the server, the server determines an appropriate address (if any) to give to the client. The server then temporarily reserves that address for the client and sends back to the client an OFFER (or DHCPOFFER) packet, with that address information. The server also configures the client’s DNS servers, WINS servers, NTP servers, and sometimes other services as well.
      5. The client sends a REQUEST (or DHCPREQUEST) packet, letting the server know that it intends to use the address.
      6. The server sends an ACK (or DHCPACK) packet, confirming that the client has a been given a lease on the address for a server-specified period of time.

    3. Question 3. What Is Dhcp Scope?

      Answer :

      DHCP scopes are used to define ranges of addresses from which a DHCP server can assign IP addresses to clients.

    4. Question 4. Types Of Scopes In Windows Dhcp?

      Answer :

      Normal Scope – Allows A, B and C Class IP address ranges to be specified including subnet masks, exclusions and reservations. Each normal scope defined must exist within its own subnet.

      Multicast Scope – Used to assign IP address ranges for Class D networks. Multicast scopes do not have subnet masks, reservation or other TCP/IP options.

      Multicast scope address ranges require that a Time To Live (TTL) value be specified (essentially the number of routers a packet can pass through on the way to its destination).

      Superscope – Essentially a collection of scopes grouped together such that they can be enabled and disabled as a single entity.

    5. Question 5. What Is Authorizing Dhcp Servers In Active Directory?

      Answer :

      1. If a DHCP server is to operate within an Active Directory domain (and is not running on a domain controller) it must first be authorized.
      2. This can be achieved either as part of the DHCP Server role installation, or subsequently using either DHCP console or at the command prompt using the netsh tool.
      3. If the DHCP server was not authorized during installation, invoke the DHCP console (Start -> All Programs -> Administrative Tools -> DHCP),
      4. right click on the DHCP to be authorized and select Authorize. 
      5. To achieve the same result from the command prompt, enter the following command:
        netsh dhcp server serverID initiate auth

      In the above command syntax, serverID is replaced by the IP address or full UNC name of system on which the DHCP server is installed.

    6. Question 6. What Ports Are Used By Dhcp And The Dhcp Clients?

      Answer :

      Requests are on UDP port 68, Server replies on UDP 67 .

    7. Question 7. List Some Benefits Of Using Dhcp?

      Answer :

      DHCP provides the following benefits for administering your TCP/IP-based network:

      Safe and reliable configuration.DHCP avoids configuration errors caused by the need to manually type in values at each computer. Also, DHCP helps prevent address conflicts caused by a previously assigned IP address being reused to configure a new computer on the network.

      Reduces configuration management.

      Using DHCP servers can greatly decrease time spent to configuring and reconfiguring computers on your network. Servers can be configured to supply a full range of additional configuration values when assigning address leases.

      These values are assigned using DHCP options. Also, the DHCP lease renewal process helps assure that where client configurations need to be updated often (such as users with mobile or portable computers who change locations frequently), these changes can be made efficiently and automatically by clients communicating directly with DHCP servers.

      The following section covers issues that affect the use of the DHCP Server service with other services or network configurations. Using DNS servers with DHCP Using Routing and Remote Access servers with DHCP Multihomed DHCP servers.

    8. Question 8. Describe The Process Of Installing A Dhcp Server In An Ad Infrastructure?

      Answer :

      Open Windows Components Wizard. Under Components , scroll to and click Networking Services. Click Details . Under Subcomponents of Networking Services , click Dynamic Host Configuration Protocol (DHCP) and then click OK.
      Click Next . If prompted, type the full path to the Windows Server 2003 distribution files, and then click Next. Required files are copied to your hard disk.

    9. Question 9. How To Authorize A Dhcp Server In Active Directory Open Dhcp?

      Answer :

      In the console tree, click DHCP

      • On the Action menu, click Manage authorized servers.
      • The Manage Authorized Servers dialog box appears. Click Authorize.
      • When prompted, type the name or IP address of the DHCP server to be authorized, and then click OK.

    10. Question 10. What Is Dhcpinform?

      Answer :

      DHCPInform is a DHCP message used by DHCP clients to obtain DHCP options. While PPP remote access clients do not use DHCP to obtain IP addresses for the remote access connection, Windows 2000 and Windows 98 remote access clients use the DHCPInform message to obtain DNS server IP addresses, WINS server IP addresses, and a DNS domain name.

      The DHCPInform message is sent after the IPCP negotiation is concluded. The DHCPInform message received by the remote access server is then forwarded to a DHCP server. The remote access server forwards DHCPInform messages only if it has been configured with the DHCP Relay Agent.

    11. Question 11. Describe The Integration Between Dhcp And Dns?

      Answer :

      Traditionally, DNS and DHCP servers have been configured and managed one at a time. Similarly, changing authorization rights for a particular user on a group of devices has meant visiting each one and making configuration changes.

      DHCP integration with DNS allows the aggregation of these tasks across devices, enabling a company’s network services to scale in step with the growth of network users, devices, and policies, while reducing administrative operations and costs. This integration provides practical operational efficiencies that lower total cost of ownership.

      Creating a DHCP network automatically creates an associated DNS zone, for example, reducing the number of tasks required of network administrators. And integration of DNS and DHCP in the same database instance provides unmatched consistency between service and management views of IP address-centric network services data.

    12. Question 12. What Protocol And Port Does Dhcp Use?

      Answer :

      DHCP, like BOOTP runs over UDP, utilizing ports 67 and 68.

    13. Question 13. Can A Dhcp Server Back Up Another Dhcp Server?

      Answer :

      You can have two or more servers handing out leases for different addresses. If each has a dynamic pool accessible to the same clients, then even if one server is down, one of those clients can lease an address from the other server. However, without communication between the two servers to share their information on current leases, when one server is down, any client with a lease from it will not be able to renew their lease with the other server.

      Such communication is the purpose of the “server to server protocol”. It is possible that some server vendors have addressed this issue with their own proprietary server-to-server communication.

    14. Question 14. What Is A Mac Address?

      Answer :

      A MAC address (also called an Ethernet address or an IEEE MAC address) is a number (typically written as twelve hexadecimal digits, 0 through 9 and A through F, or as six hexadecimal numbers separated by periods or colons, i.e. 0080002012ef, 0:80:0:2:20:ef) which uniquely identifes a computer that has an Ethernet interface.

      Unlike the IP number, it includes no indication of where your computer is located. In DHCP’s typical use, the server uses a requesting computer’s MAC address to uniquely identify it.

    15. Question 15. Can Dhcp Support Statically Defined Addresses?

      Answer :

      Yes. At least there is nothing in the protocol to preclude this and one expects it to be a feature of any DHCP server. This is really a server matter and the client should work either way. The RFC refers to this as manual allocation.

    16. Question 16. Is A Dhcp Server “supposed To” Be Able To Support A Bootp Client?

      Answer :

      The RFC on such interoperability (1534) is clear: “In summary, a DHCP server:

      MAY support BOOTP clients,” (section 2). The word “MAY” indicates such support, however useful, is left as an option. A source of confusion on this point is the following statement in section 1.5 of RFC 1541: “DHCP must provide service to existing BOOTP clients.”

      However, this statement is one in a list of “general design goals for DHCP”, i.e. what the designers of the DHCP protocol set as their own goals. It is not in a list of requirements for DHCP servers.

    17. Question 17. How Can I Relay Dhcp If My Router Does Not Support It?

      Answer :

      A server on a net(subnet) can relay DHCP or BOOTP for that net. Microsoft has software to make Windows NT do this.

    18. Question 18. What Is A Client Id?

      Answer :

      What is termed the Client ID for the purposes of the DHCP protocol is whatever is used by the protocol to identify the client computer. By default, DHCP implementations typically employ the client’s MAC address for this purpose, but the DHCP protocol allows other options. Some DHCP implementations have a setup option to specify the client ID you want. One alternative to the MAC address is simply a character string of your choice.

      In any case, in order for DHCP to function, you must be certain that no other client is using the client ID you choose, and you must be sure the DHCP server will accept it.

    19. Question 19. Is A Dhcp Client “supposed To” Be Able To Use A Bootp Server?

      Answer :

      The RFC on such interoperability (1534) is clear: “A DHCP client MAY use a reply from a BOOTP server if the configuration returned from the BOOTP server is acceptable to the DHCP client.”. The word “MAY” indicates such support, however useful, is left as an option.

    20. Question 20. How Long Should A Lease Be?

      Answer :

      A very relevant factor is that the client starts trying to renew the lease when it is halfway through: thus, for example, with a 4 day lease, the client which has lost access to its DHCP server has 2 days from when it first tries to renew the lease until the lease expires and the client must stop using the network.

      During a 2- day outage, new users cannot get new leases, but no lease will expire for any computer turned on at the time that the outage commences. Another factor is that the longer the lease the longer time it takes for client configuration changes controlled by DHCP to propogate.

    21. Question 21. What Is Dhcp Spoofing?

      Answer :

      Ascend Pipeline ISDN routers (which attach Ethernets to ISDN lines) incorporate a feature that Ascend calls “DHCP spoofing” which is essentially a tiny server implementation that hands an IP address to a connecting Windows 95 computer, with the intention of giving it an IP number during its connection process.

    22. Question 22. What Is A Dhcp Lease?

      Answer :

      A DHCP lease is the amount of time that the DHCP server grants to the DHCP client permission to use a particular IP address. A typical server allows its administrator to set the lease time.

    23. Question 23. Can Dhcp Work With Apple Talk Or Ipx?

      Answer :

      No, it is too tied to IP. Furthermore, they don’t need it since they have always had automated mechanisms for assigning their own network addresses.

    24. Question 24. Can A Bootp Client Boot From A Dhcp Server?

      Answer :

      Only if the DHCP server is specifically written to also handle BOOTP queries.

    25. Question 25. How Can I Prevent Unauthorized Laptops From Using A Network That Uses Dhcp For Dynamic Addressing?

      Answer :

      This would have to be done using a mechanism other than DHCP. DHCP does not prevent other clients from using the addresses it is set to hand out nor can it distinguish between a computer’s permanent MAC address and one set by the computer’s user. DHCP can impose no restrictions on what IP address can use a particular port nor control the IP address used by any client.

    26. Question 26. Can Dhcp Support Remote Access?

      Answer :

      PPP has its own non-DHCP way in which communications servers can hand clients an IP address called IPCP (IP Control Protocol) but doesn’t have the same flexibility as DHCP or BOOTP in handing out other parameters. Such a communications server may support the use of DHCP to acquire the IP addresses it gives out.

      This is sometimes called doing DHCP by proxy for the client. I know that Windows NT’s remote access support does this. A feature of DHCP under development (DHCPinform) is a method by which a DHCP server can supply parameters to a client that already has an IP number. With this, a PPP client could get its IP number using IPCP, then get the rest of its parameters using this feature of DHCP. SLIP has no standard way in which a server can hand a client an IP address, but many communications servers support non-standard ways of doing this that can be utilized by scripts, etc.

      Thus, like communications servers supporting PPP, such communications servers could also support the use of DHCP to acquire the IP addressees to give out. The DHCP protocol is capable of allocating an IP address to a device without an IEEE-style MAC address, such as a computer attached through SLIP or PPP, but to do so, it makes use of a feature which may or may not be supported by the DHCP server: the ability of the server to use something other than the MAC address to identify the client. Communications servers that acquire IP numbers for their clients via DHCP run into the same roadblock in that they have just one MAC address, but need to acquire more than one IP address.

      One way such a communications server can get around this problem is through the use of a set of unique pseudo-MAC addresses for the purposes of its communications with the DHCP server. Another way (used by Shiva) is to use a different “client ID type” for your hardware address. Client ID type 1 means you’re using MAC addresses. However, client ID type 0 means an ASCII string.

    27. Question 27. What Is Dhcp’s Purpose?

      Answer :

      DHCP’s purpose is to enable individual computers on an IP network to extract their configurations from a server (the ‘DHCP server’) or servers, in particular, servers that have no exact information about the individual computers until they request the information. The overall purpose of this is to reduce the work necessary to administer a large IP network. The most significant piece of information distributed in this manner is the IP address.

    28. Question 28. What Is Dora In Dhcp?

      Answer :

      • DORA – Discover, Offer , Request , Acknowledgement.
      • DORA means DHCP server Lease process short-form.

    29. Question 29. What Are The Switches Are Used With Ipconfig?

      Answer :

      IPCONFIG/ all, Release/ Renew/ FLUSHDNS

    30. Question 30. Where We Can Change The Default Dhcp Database Interval Time?

      Answer :

      We can change the default interval time for DHCP database by modifying the Registry value BackupInterval in the following location in registry

      HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesDHCPServerParameters

    31. Question 31. Dhcp Automatic Backup Default Interval Time?

      Answer :

      The interval time was 60 minutes.

    32. Question 32. What Is Dhcp Database File Extension?

      Answer :

      DHCP database file extension is .mdb

    33. Question 33. Dhcp Database Storage Default Location?

      Answer :

      SystemrootSystem32Dhcp
      example:
      C:windowssystem32dhcp

    34. Question 34. What Is Bootp?

      Answer :

      BOOTP (bootstrap protocol) is a host configuration protocol. It is developed before DHCP.

    35. Question 35. What Is Dhcpnak Message?

      Answer :

      If the Server is unable to satisfy the DHCPREQUEST message (The requested network address has been allocated) the Server Should sent DHCPNAK message to client. It can also be Sent if client's notion of network address is incorrect (Client has moved to new subnet) or client's lease expired.

    36. Question 36. What Is The Purpose Of Relay Agent?

      Answer :

      A DHCP relay agent is any host that forwards DHCP packets between clients and servers if server is not on the same physical subnet. Relay agents are used to forward requests and replies between clients and servers when they are not on the same physical subnet.DHCP relay agent can be configured using the ip helper-address command.

    37. Question 37. What Is The Reason For Getting Apipa Address?

      Answer :

      With APIPA, DHCP clients can automatically self-configure an IP address and subnetmask when a DHCP server is not available. When DHCP client boots up, it first looks for a DHCP server in order to obtain an IP address and subnet mask.A client uses the self-configured IP address until a DHCP server becomes available. The APIPA service also  checks regularly for the presence of a DHCP server. If it detects a DHCP server on the network, APIPA stops and the DHCP server replaces the APIPA networking addresses with dynamically assigned addresses.

    38. Question 38. What Is The Range Of Apipa Address?

      Answer :

      The IP address range is 169.254.0.1 through 169.254.255.254. The client also configures itself with a default Class B subnet mask of 255.255.0.0.

    39. Question 39. What Is Dhcp Decline Message?

      Answer :

      It is Sent by Client to server indicating network address is already in use (already assigned to another device).

    40. Question 40. How Dhcp Works?

      Answer :

      DHCP works on DORA Process (DISCOVER - OFFER - REQUEST - ACKNOWLEDGEMENT).

      1. When a Client needs an IP configuration, it tries to locate a DHCP server by sending a broadcast called a DHCP DISCOVER. This message will have a Destination IP of 255.255.255.255 and Destination MAC of ff:ff:ff:ff:ff:ff.[Source IP - 0.0.0.0 , Destination IP - 255.255.255.255, Source Mac - Mac address of Host, Destination Mac -FF:FF:FF:FF:FF:FF]
      2. On Receiving DHCP Discover, Server sends a DHCP OFFER message to the client. The DHCPOFFER is a proposed configuration that may include IP address, DNS server address, and lease time. This message will be unicast and have the destination mac address of DHCP client's mac address. The source mac address will be that of the DHCP server.[S.Mac - Mac address of Server , D.Mac - Mac address of Host]
      3. If the Client finds the Offer agreeable, it sends DHCP REQUEST Message requesting those particular IP parameters. This message will be a Broadcast message. [Source Mac - Mac address of Host, Destination Mac - FF:FF:FF:FF:FF:FF]
      4. The Server on receiving the DHCP REQUEST makes the configuration official by sending a unicast DHCP ACK acknowledgment.
      5. [Source Mac - Mac address of Server, Destination Mac - Mac address of Host]

    41. Question 41. What Information A Dhcp Server Can Provide To A Host?

      Answer :

      DHCP server can provide following information -

      • IP address
      • Subnet mask
      • Default gateway
      • Domain Name Server
      • WINS information

    42. Question 42. Who Created Dhcp? How Was It Created?

      Answer :

      DHCP was created by the Dynamic Host Configuration Working Group of theInternet Engineering Task Force (IETF; a volunteer organization which definesprotocols for use on the Internet). As such, it's definition is recorded in anInternet RFC and the Internet Activities Board (IAB) is asserting its status as toInternet Standardization.

      As of this writing (June 1998), DHCP is an Internet Draft Standard Protocol and is Elective. BOOTP is an Internet Draft StandardProtocol and is recommended. For more information on Internet standardization,see RFC2300 (May 1998)

    43. Question 43. How Is It Different Than Bootp Or Rarp?

      Answer :

      DHCP is based on BOOTP and maintains some backward compatibility. The maindifference is that BOOTP was designed for manual pre-configuration of the hostinformation in a server database, while DHCP allows for dynamic allocation of network addresses and configurations to newly attached hosts. Additionally,DHCP allows for recovery and reallocation of network addresses through aleasing mechanism.

      RARP is a protocol used by Sun and other vendors that allows a computer to findout its own IP number, which is one of the protocol parameters typically passedto the client system by DHCP or BOOTP. RARP doesn't support other parametersand using it, a server can only serve a single LAN. DHCP and BOOTP aredesigned so they can be routed

       

    44. Question 44. Can Dhcp Work With Appletalk Or Ipx?

      Answer :

      No, it is too tied to IP. Furthermore, they don't need it since they have alwayshad automated mechanisms for assigning their own network addresses.

    45. Question 45. How Does Dhcp And Bootp Handle Multiple Subnets?

      Answer :

      For the situations where there is more than one LAN, each with its own subnet number, there are two ways. First of all, you can set up a seperate server oneach subnet. Secondly, a feature of some routers known as "BOOTP forwarding"to forward DHCP or BOOTP requests to a server on another subnet and toforward the replies back to the client.

      The part of such a router (or server actingas a router) that does this is called a "BOOTP forwarding agent". Typically youhave to enable it on the interface to the subnet to be served and have toconfigure it with the IP address of the DHCP or BOOTP server. On a Cisco router,the address is known as the "UDP Helper Address". 

    46. Question 46. Can A Dhcp Client Boot From A Bootp Server?

      Answer :

      Only if the DHCP client were specifically written to make use of the answer froma BOOTP server. It would presumably treat a BOOTP reply as an unending leaseon the IP address.In particular, the TCP/IP stack included with Windows 95

    47. Question 47. How Can I Prevent Unauthorized Laptops From Using A Network That Usesdhcp For Dynamic Addressing?

      Answer :

      This would have to be done using a mechanism other than DHCP. DHCP does notprevent other clients from using the addresses it is set to hand out nor can itdistinguish between a computer's permanent MAC address and one set by thecomputer's user. DHCP can impose no restrictions on what IP address can use aparticular port nor control the IP address used by any client.

    48. Question 48. When Will The Server To Server Protocol Be Defined?

      Answer :

      The DHC WG of the IETF is actively investigating the issues in inter-servercommunication. The protocol should be defined "soon"

    49. Question 49. Where Is Dhcp Defined?

      Answer :

      In Internet RFCs.

    50. Question 50. Can A Dhcp Client Or Server Make A Dns Server Update The Client's Dnsentry To Match The Client's Dynamically Assigned Address?

      Answer :

      RFCs 2136 and 2137 indicate a way in which DNS entries can be updateddynamically. Using this requires a DNS server that supports this feature and aDHCP server that makes use of it. The RFCs are very recent (as of 5/97) andimplementations are few. In the mean time, there are DNS and DHCP serversthat accomplish this through proprietary means.

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