Network Addressing and Basic Troubleshooting Module 4

Checkpoint2: Network Addressing and Basic Troubleshooting Module 4 – 6 Checkpoint Exam Answers

1. A network administrator is given the network prefix 10.25.0.0/16. What subnet prefix would provide the organization with 512 subnets, each capable of supporting at least 100 hosts?

Explanation: The calculation should start with the IPv4 prefix 10.25.0.0/16, a subnet mask of 255.255.255.128 is required to create 512 subnets, each can accommodate at least 100 hosts. The subnet mask 255.255.255.128 is equivalent to the notation of /25. The difference between /16 and /25 is 9 bits. 9 bits will produce 512 subnets. A subnet mask notation /25 allows 7 bits for hosts. 7 bits provides for 126 hosts.

2. How many additional bits should be borrowed from a /26 subnet mask in order to create subnets for WAN links that need only 2 useable addresses?

Explanation: WAN links needing only 2 useable addresses use a /30 subnet, so 4 additional bits would need to be borrowed.

3. With VLSM, what prefix should be used on a network that has a planned maximum of 25 devices?

Explanation: 5 bits must be left to accommodate 25 network devices. With 5 host bits, up to 30 network devices can be placed on a network with a /27 prefix. 5 bits for hosts will yield 25=32 host addresses, but only 30 addresses are valid to be assigned to devices.

4. A network administrator is variably subnetting a given block of IPv4 addresses. Which combination of network addresses and prefix lengths will make the most efficient use of addresses when the need is for 2 subnets capable of supporting 10 hosts and 1 subnet that can support 6 hosts?

10.1.1.128/28
10.1.1.144/28
10.1.1.160/29

10.1.1.128/26
10.1.1.144/26
10.1.1.160/26

10.1.1.128/26
10.1.1.140/26
10.1.1.158/28

10.1.1.128/28
10.1.1.144/28
10.1.1.160/28

10.1.1.128/28
10.1.1.140/28
10.1.1.158/26

Explanation: Prefix lengths of /28 and /29 are the most efficient to create subnets of 16 addresses (to support 10 hosts) and 8 addresses (to support 6 hosts), respectively. Addresses in one subnet must also not overlap into the range of another subnet.

5. What subnet mask is needed if an IPv4 network has 40 devices that need IP addresses and address space is not to be wasted?

255.255.255.240
255.255.255.128
255.255.255.224
255.255.255.192
255.255.255.0

Explanation: In order to accommodate 40 devices, 6 host bits are needed. With 6 bits, 64 addresses are possible, but one address is for the subnet number and one address is for a broadcast. This leaves 62 addresses that can be assigned to network devices. The mask associated with leaving 6 host bits for addressing is 255.255.255.192.

6. A network administrator is allocated the subnet of 10.100.32.0/19 for use at a corporate site. What subnet mask can the administrator use to variably subnet the subnet into 64 new subnets?

255.255.254.0
255.255.255.128
255.255.255.0
255.255.248.0

Explanation: Creating 64 subnets requires six bits. If the subnet mask is moved six bits to the right, the new subnet mask becomes 255.255.255.128.

7. Match the IPv6 address to the IPv6 address type.

Explanation: Options matched to the correct selection.

Link-Local	Multicast	Global Unicast
FE80:0:56BA:FFEE:A0B4:47FF:FE36:532B	FF02::2	2001:DB8:10::12
FE80::1	FF02::1:FF3A:25C9	2001:DB8:A1:0B:C78::1

8. Match the description to the IPv6 addressing component.

Explanation: Place the options in the following order:

This network portion of the address is assigned by the provider.	global routing
This part of the address is used by an organization to identify subnets.	subnet ID
This part of the address is the equivalent to the host portion of an IPv4 address.	interface ID

9. A device has an IPv6 address listed as 2001:0DB8:75a3:0214:0607:1234:aa10:ba01. What is the interface ID of the device?

ba01
2001:0DB8
0607:1234:aa10:ba01
2001:0DB8:75a3

Explanation: An IPv6 address comprises 128 bits represented as eight blocks of four hexadecimal digits. The last four blocks of the address represent the interface ID and is controlled by the administrator.

10. What are two characteristics of the SLAAC method for IPv6 address configuration? (Choose two.)

The default gateway of an IPv6 client on a LAN will be the link-local address of the router interface attached to the LAN.
Router solicitation messages are sent by the router to offer IPv6 addressing to clients.
Clients send router advertisement messages to routers to request IPv6 addressing.
This stateful method of acquiring an IPv6 address requires at least one DHCPv6 server.
IPv6 addressing is dynamically assigned to clients through the use of ICMPv6.

Explanation: With SLAAC, the default gateway for IPv6 clients will be the link-local address of the router interface that is attached to the client LAN. The IPv6 addressing is dynamically assigned via the ICMPv6 protocol. SLAAC is a stateless method of acquiring an IPv6 address, a method that requires no servers. When a client is configured to obtain its addressing information automatically via SLAAC, the client sends a router solicitation message to the IPv6 all-routers multicast address FF02::2. The router advertisement messages are sent by routers to provide addressing information to clients.

11. What type of address is automatically assigned to a Cisco router interface when an IPv6 global unicast address is assigned on that interface?

loopback
unique local
link-local
broadcast

Explanation: When IPv6 is enabled on any interface, that interface will automatically generate an IPv6 link-local address.

12. Which protocol supports Stateless Address Autoconfiguration (SLAAC) for dynamic assignment of IPv6 addresses to a host?

ICMPv6
UDP
DHCPv6
ARPv6

Explanation: SLAAC uses ICMPv6 messages when dynamically assigning an IPv6 address to a host. DHCPv6 is an alternate method of assigning an IPv6 addresses to a host. ARPv6 does not exist. Neighbor Discovery Protocol (NDP) provides the functionality of ARP for IPv6 networks. UDP is the transport layer protocol used by DHCPv6.

13. An IPv6 enabled device sends a data packet with the destination address of FF02::1. What is the target of this packet?

all IPv6 configured routers on the local link
all IPv6 DHCP servers
all IPv6 enabled nodes on the local link
all IPv6 configured routers across the network

Explanation: FF02::1 is the all-nodes multicast group within the scope of the local link. A packet with this destination address is received and processed by all IPv6-enabled interfaces.

14. An IPv6 enabled device sends a data packet with the destination address of FF02::2. What is the target of this packet?

all IPv6 enabled devices across the network
all IPv6 DHCP servers
all IPv6 configured routers on the local link
all IPv6 enabled devices on the local link

Explanation: FF02::2 identifies all IPv6 routers that exist on the link or network. FF02::1 is the target for all IPv6 enabled devices on the link or network.

15. What are two ICMPv6 messages that are not present in ICMP for IPv4? (Choose two.)

Time Exceeded
Destination Unreachable
Router Advertisement
Neighbor Solicitation
Host Confirmation
Route Redirection

Explanation: ICMPv6 includes four new message types: Router Advertisement, Neighbor Advertisement, Router Solicitation, and Neighbor Solicitation.

16. Place the ICMPv6 ND messages in correct function category.

Explanation: Options matched to the correct selection.

providing address resolution	supporting dynamic address allocation and SLAAC	informing a better next-hop selection
neighbor solicitation	neighbor advertisement	router solicitation

17. An IPv6 host needs to start communication with another IPv6 host on the same network. Which message should the sending host send to find the MAC address of the destination host?

router solicitation message
neighbor advertisement message
router advertisement message
neighbor solicitation message

Explanation: When an IPv6 host needs to initiate a communications with other hosts on the same network, it sends a neighbor solicitation message to start the address resolution process.

18. An IPv6 host needs to send a message to resolve the MAC address of another host, which message would be used to start the process?

multicast neighbor solicitation message
broadcast neighbor solicitation message
multicast neighbor advertisement message
broadcast neighbor advertisement message

Explanation: When an IPv6 need to start an MAC address resolution process, the host sends a neighbor solicitation message via multicast.

19. What are three services provided by IPv6 neighbor discovery protocol? (Choose three.)

address resolution
quality of service
domain name resolving
redirection services
router discovery
IPv6 dynamic routing

Explanation: IPv6 Neighbor Discovery protocol, also referred to as ND or NDP, provides address resolution, router discovery, and redirection services for IPv6 using ICMPv6.

20. IPv6 host A is sending a neighbor solicitation message to IPv6 host B on the same Ethernet network. What type of address is used in the Destination MAC field of the Ethernet frame header?

a multicast MAC address associated with the destination IPv6 address information
a multicast MAC address associated with the sending host IPv6 address information
the special MAC broadcast address reserved for neighbor discover protocol
an anycast MAC address reserved for neighbor discover protocol

Explanation: When an IPv6 host sends a neighbor solicitation message to another IPv6 host on the same Ethernet network, the sending host creates an Ethernet frame and add a multicast MAC address in the Destination MAC address field. This multicast MAC address maps the special solicited-node multicast address derived from the destination IPv6 address.

21. Which ICMPv6 message type contains network configuration information for clients that are performing SLAAC?

neighbor advertisement
router solicitation
router advertisement
neighbor solicitation

Explanation: When performing SLAAC, IPv6 clients receive network configuration information from router advertisement messages that are sent by a local router.

22. A network administrator wants to have the same subnet mask for three subnetworks at a small site. The site has the following networks and numbers of devices:

Subnetwork A: IP phones – 10 addresses
Subnetwork B: PCs – 8 addresses
Subnetwork C: Printers – 2 addresses

What single subnet mask would be appropriate to use for the three subnetworks?

255.255.255.252
255.255.255.240
255.255.255.248
255.255.255.0

Explanation: If the same mask is to be used, then the network with the most hosts must be examined for number of hosts. Because this is 10 hosts, 4 host bits are needed. The /28 or 255.255.255.240 subnet mask would be appropriate to use for these networks.

23. Which string of hexadecimal numbers is an IPv6 GUA Interface ID probably created by using the EUI-64 process?

fe99:47ff:fe75:cee0
00:12:ff:eb:6b:40
52:74:fe:be:a8:7f
1272:23ff:eef0:1639

Explanation: An easy way to identify that an address was probably created by using EUI-64 is the fffe located in the middle of the interface ID.

24. An IPv6 host receives a MAC address resolution request. Which message would the host send back in responding to the request?

neighbor solicitation message
router solicitation message
router advertisement message
neighbor advertisement message

Explanation: When an IPv6 host receives an ICMPv6 neighbor solicitation message for MAC address resolution, the host returns a neighbor advertisement message to provide the MAC address.