CCNA 2 Routing and Switching Essentials v5 Chapter 10: DHCP – Check Your Understanding Questions Answers
1. Which statements are true about the DHCP server functions? (Choose two.)
- When a client requests an IP address, the DHCP server searches the binding table for an entry that matches the client’s MAC address. If an entry exists, the corresponding IP address for the entry is returned to the client.
- Clients can be assigned an IP address from a predefined DHCP pool for a finite lease period.
- DHCP services must be installed on a dedicated network server to define the pool of IP addresses available to the client.
- The DHCP server can answer requests and assign IP addresses for a particular subnet only.
- Each subnet in the network requires a dedicated DHCP server to assign IP addresses to the host on the subnet.
- DHCP provides clients with an IP address, a subnet mask, a default gateway, and optionally, a domain name.
Explanation: DHCP can provide the IP address, subnet mask, default gateway, domain name, DNS server, NetBIOS, and WINS server. The duration of the DHCP lease is by default 1 day, but you can change it by using the lease command.
2. Consider the following configuration:
Rl(config)# ip dhcp pool 192.168.10.0
What is the function of the 192.168.10.0 argument?
- Name of the DCHP pool
- Pool of IP addresses available for lease
- Range of excluded IP addresses
- Subnet where the DHCP server resides
Explanation: The argument that follows the command ip dhcp pool is the pool-name argument.
3. Which three statements about DHCPv4 are true? (Choose three.)
- DHCP messages use UDP as a transport protocol.
- The DHCPOFFER message is sent by a DHCP server after receiving a DHCPDISCOVER message from a client.
- DHCP uses ports 67 and 68.
- The DHCPREQUEST message is sent by a DHCP client to locate a DHCP server.
- The DHCPACK message is sent by the DHCP server to provide the DHCP client with the DHCP server MAC address for further communications.
- All DHCP communications are broadcast.
Explanation: DHCP uses User Datagram Protocol (UDP) as its transport protocol. The client sends messages to the server on port 67. The server sends messages to the client on port 68. When the DHCP server receives a DHCPDISCOVER message, it finds an available IP address to lease, creates an ARP entry consisting of the MAC address of the requesting host and the leased IP address, and transmits a binding offer with a DHCPOFFER message. The DHCPOFFER message is sent as a unicast, using the server’s Layer 2 MAC address as the source address and the client’s Layer 2 address as the destination.
4. Refer to the exhibit. If PC3 used R1 as a DHCPv4 server, on what interface would the ip helper-address be configured?
- R3 S0/0/0
- Any interface on R3
- R3 S0/0/1
- R3 G0/0
Explanation: The helper address (DHCPv4 relay) should be configured on the interface that hears the DHCP broadcast. Otherwise, the DHCP broadcast will be dropped by the router.
5. If a DHCPv6 client resides on subnet 192.168.30.0/24 and the DHCPv6 server resides on subnet 192.168.10.0/24, why is it necessary for a DHCPv6 Relay Agent?
- Because DHCPv6 does not use broadcasts
- Because a DHCPv6 client cannot use a DHCP server on a remote network
- Because DHCPv6 messages still need to be relayed if the DHCPv6 server resides on a different network
- Because DHCP v6 messages must be converted to a broadcast to be heard across multiple networks
Explanation: DHCPv6 relay is still used when the DHCPv6 server is on a different link than the client.
6. Which two methods of assigning an IPv6 address to a router interface are automatic and can be used in conjunction with one another? (Choose two.)
- EUI-64
- Static assignment
- DNS
- DHCPv6
- Stateless autoconfiguration
Explanation: Stateless autoconfiguration automatically configures the IPv6 address for the host, and DHCPv6 enables the automatic allocation of reusable network addresses. DHCPv6 is a stateful counterpart to IPv6 stateless autoconfiguration. It can be used separately or concurrently with IPv6 stateless autoconfiguration to obtain configuration parameters.
7. Place the four DHCPv4 steps in the order they occur. Note that not all options will be used.
DHCPREQUEST
DHCPLEASE
DHCPACK
DHCPDISCOVER
DHCPREPLY
DHCPOFFER
First: _____________________________
Second: ___________________________
Third: _____________________________
Fourth: ____________________________
| First | DHCPDISCOVER |
| Second | DHCPOFFER |
| Third | DHCPREQUEST |
| Fourth | DHCPACK |
Explanation: The four message types in order are as follows: DHCP Discover, DHCP Offer, DHCP Request, and DHCP Acknowledgment.
8. Which DHCP message types are originated by a DHCPv4 server? (Select all that apply.)
- DHCPREQUEST
- DHCPLEASE
- DHCPACK
- DHCPDISCOVER
- DHCPREPLY
- DHCPOFFER
Explanation: The DHCPv4 process starts with a client sending a DHCPDISCOVER to probe for a DHCPv4 server using a broadcast message. When a DHCPv4 server hears the discover message, the server reserves an available IPv4 address for the client and creates an ARP entry containing the client MAC address. The server responds with a DHCPOFFER message. The client responds to the server with a DHCP request. The server responds with a DHCPACK (acknowledgment) message.
9. What type of IPv6 message is used by an IPv6 host to automatically obtain an IPv6 address from a router?
- broadcast
- DNS
- RS
- ARP
Explanation: The Router Solicitation (RS) message is sent by a client when it obtains addressing information automatically using stateless address autoconfiguration (SLAAC).
10. Which DHCPv6 option is most like DHCPv4?
- SLAAC
- Stateful DHCPv6
- Stateless DHCPv6
- EUI-64
Explanation: SLAAC is used when the client automatically receives basic IP addressing configuration from the router. Stateless DHCPv6 is when the client automatically gets IP addressing information but uses the DHCPv6 server for additional configuration information.
11. Match the DHCPv6 command with the purpose. Note that not all options are used.
_______ Enables IPv6 routing.
_______ RA messages sent to an interface with this command indicates that additional information is available from a stateless DHCPv6 server.
_______ Used on a router interface connected to a DHCPv6 client, and the DHCPv6 server is on a different link.
_______ Causes a router interface to request a DHCPv6 address.
_______ RA messages sent to an interface with this command indicates that the client is to obtain IP addressing information from a stateful DHCPv6 server.
- ipv6 nd other-config-flag
- ipv6 dhcp relay destination
- ipv6 dhcp
- ipv6 unicast-routing
- ipv6 nd managed-config-flag
- ipv6 routing
- ipv6 address dhcp
| ipv6 unicast-routing | Enables IPv6 routing. |
| ipv6 nd other-config-flag | RA messages sent to an interface with this command indicates that additional information is available from a stateless DHCPv6 server. |
| ipv6 dhcp relay destination | Used on a router interface connected to a DHCPv6 client, and the DHCPv6 server is on a different link. |
| ipv6 address dhcp | Causes a router interface to request a DHCPv6 address. |
| ipv6 nd managed-config-flag | RA messages sent to an interface with this command indicates that the client is to obtain IP addressing information from a stateful DHCPv6 server. |
Explanation: The ICMPv6 RA message contains two flags that indicate which IPv6 addressing option the client should use: the Managed Address Configuration (M) flag
and the Other Configuration (O) flag. When stateful DHCPv6 is to be used, the M flag
is set and the O flag is not used. When stateless DHCPv6 is used, the O flag is enabled
(set) and the M flag is left at the default setting of disabled or 0.
12. What are the two port numbers used by DHCPv6? (Choose two.)
- 67
- 68
- 546
- 547
- 1025
- 1026
- 34768
- 34769
Explanation: DHCPv4 uses UDP ports 67 and 68. DHCPv6 uses UDP ports 546 and 547.