DHCP Interview Questions for freshers experienced :-
1. What is DHCP?
Dynamic Host Configuration Protocol: assigns IPs to the clients requested dynamically or automatically.
2. Describe the process of installing a DHCP server in an AD infrastructure ?
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.
3. Process of DHCP (DORA)?
- Discover: The Client discovers DHCP
- Offers: The DHCP server offers a group of IPs to the clients to pick any
- Request: The client selects an IP and request DHCP to confirm it
- Acknowledgement: The DHCP server makes a confirmation by sending an DHCPPACK to the client.
4. How to authorize a DHCP server in Active Directory Open DHCP ?
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.
5. What is a Scope?
Range of IP Addresses.
6. What is DHCPINFORM ?
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.
7. What is an IP Lease?
DHCP server clients an IP to the client for a period of 8 days. This offer is called IP Lease.
8. Describe the integration between DHCP and DNS?
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.
9. What is the default duration of a lease?
8 Days.
10. How does DHCP and BOOTP handle multiple subnets?
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 on each subnet. Secondly, a feature of some routers known as “BOOTP forwarding” to forward DHCP or BOOTP requests to a server on another subnet and to forward the replies back to the client. The part of such a router (or server acting as a router) that does this is called a “BOOTP forwarding agent”. Typically you have to enable it on the interface to the subnet to be served and have to configure it with the IP address of the DHCP or BOOTP server. On a Cisco router, the address is known as the “UDP Helper Address”.
11. What is authentication DHCP server?
Enabling AD Know the availability of DHCP server Useful when we have multiple DHCP Server and you want to you designate one particular DHCP server to be active. Then we should authorize.
12. What ports are used by DHCP and the DHCP clients ?
- UDP Port 68 used for Requests.
- UDP Port 67 used for server Replies.
13. What is IP Reservation?
Resolving a particular dynamic IP for a particularly system.
14. How can I prevent unauthorized laptops from using a network that uses DHCP for dynamic addressing?
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.
15. What is exclusion?
Omitting assigning from the range selected IPs.
16. Can DHCP work with AppleTalk or IPX?
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.
17. What is a SUPER SCOPE?
Group of scopes is called as super scope.
18. Can DHCP support statically defined addresses?
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.
19. Purpose of DHCP Relay agent?
DHCP server is available on another N/W and you want another N/W to obtain IPs from the DHCP server. Then the DHCP, RA can forward the request from the clients to the DHCP server to obtain IPs for the clients it acts like a mediator between clients and DHCP.
20. When will the server to server protocol be defined?
The DHC WG of the IETF is actively investigating the issues in inter-server communication. The protocol should be defined “soon”.
21. What Is Dhcp Spoofing?
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. What Is A Dhcp Lease?
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. Can Dhcp Work With Apple Talk Or Ipx?
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. Can A Bootp Client Boot From A Dhcp Server?
Only if the DHCP server is specifically written to also handle BOOTP queries.
25. How Can I Prevent Unauthorized Laptops From Using A Network That Uses Dhcp For Dynamic Addressing?
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. Can Dhcp Support Remote Access?
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. What Is Dhcp’s Purpose?
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. What Is Dora In Dhcp?
- DORA – Discover, Offer , Request , Acknowledgement.
- DORA means DHCP server Lease process short-form.
29. What Are The Switches Are Used With Ipconfig?
IPCONFIG/ all, Release/ Renew/ FLUSHDNS
30. Where We Can Change The Default Dhcp Database Interval Time?
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. Dhcp Automatic Backup Default Interval Time?
The interval time was 60 minutes.
32. What Is Dhcp Database File Extension?
DHCP database file extension is .mdb
33. Dhcp Database Storage Default Location?
SystemrootSystem32Dhcp
example:
C:windowssystem32dhcp
34. What Is Bootp?
BOOTP (bootstrap protocol) is a host configuration protocol. It is developed before DHCP.
35. What Is Dhcpnak Message?
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. What Is The Purpose Of Relay Agent?
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. What Is The Reason For Getting Apipa Address?
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. What Is The Range Of Apipa Address?
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. What Is Dhcp Decline Message?
It is Sent by Client to server indicating network address is already in use (already assigned to another device).
40. How Dhcp Works?
DHCP works on DORA Process (DISCOVER – OFFER – REQUEST – ACKNOWLEDGEMENT).
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]
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]
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]
The Server on receiving the DHCP REQUEST makes the configuration official by sending a unicast DHCP ACK acknowledgment.
[Source Mac – Mac address of Server, Destination Mac – Mac address of Host]
41. What Information A Dhcp Server Can Provide To A Host?
DHCP server can provide following information –
- IP address
- Subnet mask
- Default gateway
- Domain Name Server
- WINS information
42. Who Created Dhcp? How Was It Created?
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. How Is It Different Than Bootp Or Rarp?
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. Can Dhcp Work With Appletalk Or Ipx?
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. How Does Dhcp And Bootp Handle Multiple Subnets?
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. Can A Dhcp Client Boot From A Bootp Server?
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. How Can I Prevent Unauthorized Laptops From Using A Network That Usesdhcp For Dynamic Addressing?
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. When Will The Server To Server Protocol Be Defined?
The DHC WG of the IETF is actively investigating the issues in inter-servercommunication. The protocol should be defined “soon”
49. Where Is Dhcp Defined?
In Internet RFCs.
50. Can A Dhcp Client Or Server Make A Dns Server Update The Client’s Dnsentry To Match The Client’s Dynamically Assigned Address?
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.
More DHCP Interview Questions :-
51. How Long Should A Lease Be?
52. List Some Benefits Of Using DHCP?
53. What Is BootP?
54. Can DHCP Support Remote Access?
55. Can you limit which MAC addresses are allowed to roam?
56. What Is The Range Of APIPA Address?
57. What other sources of information are available?
58. What Is DHCPNak Message?
59. What Is The Purpose Of Relay Agent?
60. What is DHCPNAK message?
61. How Is It Different Than BootP Or RARP?
62. Can DHCP Work With AppleTalk Or IPX?
63. How Does DHCP And BootP Handle Multiple Subnets?
64. What Is The DHCP Process For Client Machine?
65. What Is DHCP Decline Message?
66. How DHCP Works?
67. What Information A DHCP Server Can Provide To A Host?
68. What Ports Are Used By DHCP And The DHCP Clients?
69. How can I run Windows 95 without a DHCP server?
70. What Is DHCP Spoofing?
71. What Is A DHCP Lease?
72. How To Authorize A DHCP Server In Active Directory Open DHCP?
73. How Can I Prevent Unauthorized Laptops From Using A Network That Uses DHCP For Dynamic Addressing?
74. Is there an SNMP MIB for DHCP?
75. What Routers include DHCP servers?
76. What are the DHCP plans of major client-software vendors?
77. What freeware DHCP clients are available?
78. What features or restrictions can a DHCP server have?
79. What freeware DHCP servers are available?
80. How Long Should A Lease Be?