4.6 Dynamic Host Config Protocol (DHCP)

Question 1

What is DHCP?

Answer 1

A protocol used by hosts to obtain various parameters necessary for the clients to operate in a network

Question 2

What is an address pool

Answer 2

the range of addresses that can be assigned to requesting hosts.

Question 3

What is a lease

Answer 3

length of time for which the assignment is valid. It contains the assigned IP address and other information for the client.

Question 4

What are 4 DHCP options

Answer 4

Domain Name Server (DNS) server address(es)
Default router (or default gateway) address
Windows Internet Name Service (WINS) server addresses
Additional TCP/IP configuration parameters

Question 5

What is binding

Answer 5

is an association of a MAC address with a specific IP address

Question 6

What is an interface

Answer 6

The interface that responds to DHCP requests is identified automatically according to the IP address assigned to the interface.

Question 7

What is the first step in the DHCP client process

Answer 7

Lease Request - The client initializes a limited version of TCP/IP and broadcasts a DHCPDISCOVER packet requesting the location of a DHCP server.

Question 8

What is the second step in the DHCP Client Process?

Answer 8

Lease offer - All DHCP servers with available IP addresses send DHCPOFFER packets to the client. These include the client’s hardware address, the IP address the server is offering, the subnet mask, the duration of the IP lease, and the IP address of the DHCP server making the offer.

Question 9

What is the third step in the DHCP Client Process?

Answer 9

Lease selection - The client selects the IP address from the first offer it receives and broadcasts a DHCPREQUEST packet requesting to lease the IP address in that offer.

Question 10

What is the last step in the DHCP Client Process?

Answer 10

IP Lease Acknowledgement - The DHCP server that made the offer responds and all other DHCP servers withdraw their offers. The IP addressing information is assigned to the client and the offering DHCP server sends a DHCPACK (acknowledgement) packet directly to the client. The client finishes initializing and binding the TCP/IP protocol.

Question 11

Why would you enable DHCP acroos subnets

Answer 11

Because DHCP leases uses frame-level broadcasts and they don’t pass through routers to other subnets

Question 12

How do you enable dhcp across subnets

Answer 12

Enable BOOTP (DHCP broadcast) requests through the router.
Configure a computer for BOOTP forwarding to request IP information on behalf of other clients.

Question 13

Describe ARP

Answer 13

Used by hosts to discover the MAC address of a computer from its IP address.

Question 14

Describe Reverse Address Resolution Protocol (RARP)

Answer 14

Used by a host to discover the IP address of a computer from its MAC address.

Question 15

Describe Bootstrap Protocol (BOOTP)

Answer 15

Used by a host (such as a diskless workstation) to query a bootstrap computer and receive an IP address assignment. A BOOTP server has a static list of MAC addresses and their corresponding IP addresses.

Question 16

What is the first step in the DHCP configuration process

Answer 16

Identify an external database agent with a URL.

Question 17

What is the second step in the DHCP Pre-configuration process

Answer 17

Identify the IP address range to be assigned by the DHCP server

Question 18

What is the third step in the DHCP Pre-configuration process

Answer 18

Identify DHCP options where necessary.

Question 19

What is the fourth step in the DHCP Pre-configuration process

Answer 19

Identify the DNS domain name.

Question 20

What does the command Router(config)#service dhcp do

Answer 20

Enables DHCP features on the router.

Question 21

What does the command Router(config)#no ip dhcp conflict logging do

Answer 21

Prevents an address from being assigned by the DHCP server.

Question 22

Router(config)#ip dhcp pool [VLAN_ID]

Answer 22

Configures a DHCP address pool on the specified VLAN

Question 23

Router(dhcp-config)#network [address] [mask

Answer 23

Sets the network address and subnet mask for a DHCP address pool.

Question 24

Router(dhcp-config)#domain-name [domain]

Answer 24

Sets the domain name to be delivered to DHCP clients.

Question 25

Router(dhcp-config)#dns-server [server1_ip] [server2_ip]

Answer 25

Sets the DNS server address to be delivered to DHCP clients

Question 26

Router(dhcp-config)#default-router [router_ip]

Answer 26

Sets the default router address to be delivered to DHCP clients

Question 27

Router(dhcp-config)#lease [days]

Answer 27

Sets the lease duration (in days) for a DHCP address pool.

Question 28

Router(dhcp-config)#host [address] [mask]

Router(dhcp-config)#client-identifier [mac_address]

Answer 28

Manually binds a specific IP address and mask to a host.

Question 29

Router(config-subif)#ip helper-address [address]

Answer 29

Enables the DHCP relay agent feature.

Question 30

no ip forward-protocol udp [port]

Answer 30

Controls which broadcast packets and protocols are forwarded by a DHCP relay agent.

Question 31

Router#show ip dhcp binding

Answer 31

Displays information about each IP address lease.

Question 32

Router#show ip dhcp pool [pool_name]

Answer 32

Displays information about the DHCP address pools, including the following:

Question 33

Router#show ip dhcp server statistics

Answer 33

Displays DHCP server statistics.

Question 34

Router#show ip dhcp conflict

Answer 34

Displays IP addresses with conflicts as well as the method used to identify them:

Question 35

clear ip dhcp conflict

Answer 35

Clears the address conflict list.

Question 36

Router#show ip dhcp database

Answer 36

Displays DHCP server database agent information, including the following:

Question 37

Router#show hosts

Answer 37

Displays the default domain name, the style of name lookup service, a list of name server hosts, and the cached list of hostnames and addresses.

Question 38

Router(config)#interface vlan 1

Router(config-if)#ip address dhcp

Answer 38

Configures an interface on a Cisco device to get its IP address from the DHCP server

Question 39

use ip dhcp excluded-address [ip address - ip address
use ip dhcp pool cisco to enter dhcp conifg
to configure dns type ip adress of dns server use dns-server [server ip address]