7.1: DHCPv4 Concepts

Question 1

___ assigns IPv4 addresses and other network configuration information dynamically.
It is an extremely useful and timesaving tool for network administrators

Answer 1

Dynamic Host Configuration Protocol v4 (DHCPv4)

Question 2

In a small branch or SOHO location, a Cisco router can be configured to provide DHCPv4 services without the need for a _______

Answer 2

dedicated server

Question 3

True or false
The DHCPv4 server does not dynamically assigns, or leases, an IPv4 address from a pool of addresses for a limited period of time chosen by the server, or until the client no longer needs the address.

Answer 3

False
The DHCPv4 server dynamically assigns, or leases, an IPv4 address from a pool of addresses for a limited period of time chosen by the server, or until the client no longer needs the address.

Question 4

Administrators configure DHCPv4 servers to set the ____ to time out at different intervals.

Answer 4

leases

Question 5

The lease is typically anywhere from 24 hours to a week or more. When the lease expires, the client must ____

Answer 5

ask for another address, although the client is typically reassigned the same address

Question 6

DHCPv4 works in a ___ mode.

Answer 6

client/server

Question 7

DHCPv4 operation

Answer 7

1. Client communicates with a DHCPv4 server and the server assigns or leases an IPv4 address to that client
2. The client connects to the network with that leased IPV4 address until the lease expires
3. Client must contact the DHCP server periodically to extend the lease
4. The lease mech ensure that the client doesn’t keep the IPV4 address if not needed
5. When the lease expires, the DHCP server returns the address to the pool where it can be reallocated as necessary

Question 8

Steps to obtain lease

Answer 8

1. DHCP Discover (DHCPDISCOVER)
2. DHCP Offer (DHCPOFFER)
3. DHCP Request (DHCPOFFER)
4. DHCP Acknowledgment (DHCPPACK)

Question 9

Step 1. DHCP Discover (DHCPDISCOVER)
The client starts the process using a broadcast DHCPDISCOVER message with its own ___ to discover available DHCPv4 servers.

Answer 9

MAC address

Question 10

Step 1. DHCP Discover (DHCPDISCOVER)
Because the client has no valid IPv4 information at bootup, it uses ___ to communicate with the server.

Answer 10

Layer 2 and Layer 3 broadcast addresses

Question 11

The purpose of the DHCPDISCOVER message is to _____

Answer 11

find DHCPv4 servers on the network

Question 12

Step 2. DHCP Offer (DHCPOFFER)
When the DHCPv4 server receives a DHCPDISCOVER message, it reserves an available ____ to lease to the client.

Answer 12

IPv4 address

Question 13

Step 2. DHCP Offer (DHCPOFFER)
The server also creates an ___ consisting of the MAC address of the requesting client and the leased IPv4 address of the client.

Answer 13

ARP entry

Question 14

Step 2. DHCP Offer (DHCPOFFER)
The DHCPv4 server sends the binding ___message to the requesting client.

Answer 14

DHCPOFFER

Question 15

Step 3. DHCP Request (DHCPREQUEST)
When the client receives the DHCPOFFER from the server, it sends back a ______.

Answer 15

DHCPREQUEST message

Question 16

This message is used for both lease origination and lease renewal.

Answer 16

DHCPREQUEST

Question 17

When used for lease origination, the DHCPREQUEST serves as a ____to the selected server for the parameters it has offered and an ____to any other servers that may have provided the client a binding offer.

Answer 17

binding acceptance notice
implicit decline

Question 18

TRUE OR FALSE
The DHCPREQUEST message is sent in the form of a broadcast to inform this DHCPv4 server and any other DHCPv4 servers about the accepted offer.

Answer 18

TRUE

Question 19

Step 4. DHCP Acknowledgment (DHCPACK)
On receiving the DHCPREQUEST message, the server may verify the lease information with an___ to that address to ensure it is not being used already, it will create a new ARP entry for the client lease, and reply with a ____ message.

Answer 19

ICMP ping
DHCPACK

Question 20

___ is a duplicate of the DHCPOFFER, except for a change in the message type field

Answer 20

DHCPPACK

Question 21

Step 4. DHCP Acknowledgment (DHCPACK)
When the client receives the DHCPACK message, it logs the ___ and may perform an ARP lookup for the assigned address.

Answer 21

configuration information

Question 21

Step 4. DHCP Acknowledgment (DHCPACK)
When the client receives the DHCPACK message, it logs the ___ and may perform an ARP lookup for the assigned address.

Answer 21

configuration information

Question 22

Step 4. DHCP Acknowledgment (DHCPACK)
When the client receives the DHCPACK message, it logs the ___ and may perform an ARP lookup for the assigned address.

Answer 22

configuration information

Question 23

Step 4. DHCP Acknowledgment (DHCPACK)
When the client receives the DHCPACK message, it logs the ___ and may perform an ARP lookup for the assigned address.

Answer 23

configuration information

Question 24

True or false
If there is a reply to the ARP, the client knows that the IPv4 address is valid and starts using it as its own.

Answer 24

False
If there is no reply to the ARP, the client knows that the IPv4 address is valid and starts using it as its own.

Question 25

Steps to renew a lease

Answer 25

1. DHCP Request (DHCPREQUEST)
2. DHCP Acknowledgment (DHCPACK)