Final-Exam: Network Addressing and Basic Troubleshooting Final Test Online

Hint

Place the options in the following order:

location of a desktop PC in a classroom	physical topology diagram
path of cables that connect rooms to wiring closets	physical topology diagram
IP address of a server	logical topology diagram

Hint

The default gateway for host H1 is the router interface that is attached to the LAN that H1 is a member of. In this case, that is the G0/0 interface of R1. H1 should be configured with the IP address of that interface in its addressing settings. R1 will provide routing services to packets from H1 that need to be forwarded to remote networks.

Hint

Fiber-optic cables provide immunity to both EMI and RFI and a single cable can extend for several miles before regeneration is needed.

Hint

Legacy bus-topology Ethernet LAN uses CSMA/CD as network media access control protocol. It works by detecting a collision in the medium and backing off (after transmitting a jam signal) as necessary. When one host wants to transmit a frame, it listens on the medium to check if the medium is busy. After it senses that no one else is transmitting, the host starts transmitting the frame, it also monitors the current level to detect a collision. If it detects a collision, it transmits a special jam signal so that all other hosts can know there was a collision. The other host will receive this jam signal and stop transmitting. After this, both hosts enter an exponential backoff phase and retry transmission.

Hint

Physical topology refers to the physical connection and how hosts, switches, and routers are physically connected. Logical topology refers to how nodes transfer frames through virtual connections and how the upper layers perceive the network.

Hint

On a Windows host, either the route print or netstat -r commands can be used to display the host routing table. The show ip route command is used on a router to display its routing table. The netstat –s command is used to display per-protocol statistics. The tracert command is used to display the path that a packet travels to its destination.

Hint

The default gateway is used to route packets destined for remote networks. The default gateway IP address is the address of the first Layer 3 device (the router interface) that connects to the same network.

Hint

Options matched to the correct selection.

Multimode Fiber	Single-mode Fiber
LED as light source	only one ray of light into the fiber
several paths of light into the fiber	generally used with Campus backbone
generally used with LANs	laser as light source

Hint

The fact that the user can access a file share resource but not the internet indicates the issue might be caused by default gateway misconfiguration. If no default gateway is configured in the host TCP/IP settings, or if the wrong default gateway is specified, messages addressed to hosts on the internet cannot be delivered.

Hint

Ethernet uses CSMA/CD as the access control method. With CSMA/CD, each end device monitors the media for the presence of a data signal. If the media is free, the device can transmit data immediately. The other options are operations with CSMA/CA and Token passing.

Hint

A router interface that has been configured with IPv6 addressing information responds to a router solicitation (RS) message with a router advertisement (RA) message. The RA message is used in the IPv6 stateless address autoconfiguration (SLAAC) process and the message contains the local prefix and prefix length of the local segment such as 2001:db8:acad:1::/64.

Hint

IPv6 does not use ARP. Instead, ICMPv6 neighbor discovery is used by sending neighbor solicitation and neighbor advertisement messages.

Hint

The subnet mask of 255.255.255.0 has 8 host bits. The mask of 255.255.255.128 results in 7 host bits. The mask of 255.255.255.224 has 5 host bits. Finally, 255.255.255.240 represents 4 host bits.

Hint

This address is one of the assigned IPv6 multicast addresses. Packets addressed to FF02::1 are for all IPv6 enabled devices on the link or network. FF02::2 is for all IPv6 routers that exist on the network.

Hint

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

Hint

Place the options in the following order:

router advertisement message	provides network addressing information
neighbor advertisement message	provides MAC address information of a host
router solicitation message	requests network addressing information
neighbor solicitation message	requests MAC address of the destination host

Hint

The valid numbers that can be used with a /26 mask include 172.16.0.0/26, 172.16.0.64/26, 172.16.0.128/26, and 172.16.0.192/26.

Hint

The network portion, or prefix, of an IPv6 address is identified through the prefix length. A /64 prefix length indicates that the first 64 bits of the IPv6 address is the network portion. Hence the prefix is 2001:DB8:BC15:A.

Hint

Place the options in the following order:

Network C	192.168.0.96 /27
Network A	192.168.0.128 /25
Network D	192.168.0.80 /30
Network B	192.168.0.0 /26

Hint

When a router receives a data packet, it may analyze the best gateway device that the host should use. When there are multiple gateway devices available on a network, an IPv6 router will send ICMPv6 redirect messages to the sending host if it determines that there is a more efficient path for the transmissions.

Hint

A router contains four types of memory: RAM – volatile memory used to store the running IOS, running configuration file, routing table, ARP table, as well as serve as a packet buffer ROM – nonvolatile memory used to hold a limited version of the IOS, bootup instructions, and basic diagnostic software NVRAM – nonvolatile memory used to hold the startup configuration file Flash – nonvolatile memory used to hold the IOS and other system files

Hint

Place the options in the following order:

phase 2	locate and load the Cisco IOS software
phase 3	locate and load the startup configuration file
phase 1	perform the POST and load the bootstrap program

Hint

Physical problems are concerned mainly with the hardware aspects of computers and networking devices, and the cables that interconnect them. Physical problems do not include the logical (software) configuration of devices.

Hint

A switch booting to the Switch> prompt indicates that the switch booted normally. This means a the switch successfully completed POST full version of the Cisco IOS was loaded.

Hint

The Command Prompt command tracert will map the path from the PC to the web server and measure transit delays of packets across the network.

Hint

RAM stores data that is used by the device to support network operations. The running configuration is stored in RAM. This type of memory is considered volatile memory because data is lost during a power cycle. Flash memory stores the IOS and delivers a copy of the IOS into RAM when a device is powered on. Flash memory is nonvolatile since it retains stored contents during a loss of power.

Hint

The nslookup command can be used to troubleshoot name resolution issues and to verify the current status of the name servers. The nslookup output identifies the default DNS server that is configured on the host. The utility has many options available for testing and verification of the DNS process.

Hint

The show startup-config command displays the saved configuration located in NVRAM. The show running-config command displays the contents of the currently running configuration file located in RAM.​

Hint

Physical topologies show the physical interconnection of devices. Logical topologies show the way the network will transfer data between connected nodes.

Hint

With the copy running-config startup-config command, the content of the current operating configuration replaces the startup configuration file stored in NVRAM. The configuration file saved in NVRAM will be loaded when the device is restarted.

Hint

The physical layer standards address three functional areas: physical components, encoding, and signaling. Frame encapsulation, media access control, and error detection and retransmission are services provided by the data link layer.

Hint

RFI, EMI, and crosstalk cause interference to the electrical signals that are transmitted through copper cables. Both UTP and STP use twisted pairs of wires that help protect against crosstalk. However, STP provides greater protection against RFI and EMI than UTP provides.

Hint

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

Hint

The network address 172.16.0.0 has a default mask of 255.255.0.0 (/16). This address has 16 bits in the network portion and 16 bits in the host portion. To have at least 500 subnets, you need to borrow 9 bits (subnets) from the host portion (2^9 = 512 subnets), leaving 7 bits to create hosts. Thus the resulting netmask is 255.255.255.128, and the number of hosts per subnet is 2^7 = 128 – 2 = 126 hosts.

Hint

The interface ID of an IPv6 address is the rightmost 64 bits, or last four hextets, of the address if no interface ID bits have been used for subnets.

Hint

To derive the EUI-64 interface ID by using the MAC address 1C-6F-65-C2-BD-F8, three steps are taken.

1. Change the seventh bit of the MAC address from a binary 0 to a binary 1 which changes the hex C, into a hex E.
2. Insert hex digits FFFE into the middle of the address.
3. Rewrite the address in IPv6 format.

The three steps, when complete, give the interface ID of 1E6F:65FF:FEC2:BDF8.

Hint

The netstat command displays active TCP connections that are open and running on a networked host. The netstat command lists the protocol in use, the local address and port number, the foreign address and port number, and the state of the connection.

Hint

The ipconfig and nslookup commands will provide initial IP address and DNS configuration information to the technicians and determine if DHCP is assigning correct information to the PCs. The ping utility would be used to verify, or not, connectivity to the default gateway (router) using the configured default gateway address, or using the known correct default gateway address if these are found to be different. The arp -a or netsh interface ipv6 show neighbor commands could be used if the problem is then suspected to be an IP address to MAC address mapping issue. The telnet and tracert utilities could be used to determine where the problem was located in the network if the default gateway configuration was found to be correct.

Hint

A successful ping to the default gateway assigned to a PC is an indicator that the PC can communicate across the network. The default gateway must be on the same IP network as the PC, and is usually the IP address of the router interface connected to the same physical network as the PC.

Hint

The exhibit shows a logical topology diagram for the network design. The network design features shown in this diagram includes flow of information in the network including addressing, network devices that might be needed, and network segmentation provisioned through a router. The suggested IP address blocks are with the default subnet mask, no subnetting is required. While network devices are grouped logically in the diagram, the locations are not determined or indicated. Routing will be required, but there is no indication of which routing protocol should be used.

Hint

The largest subnet requires 500 hosts addresses, so the most efficient subnet would be a /23 with the mask 255.255.254.0. The smallest subnet, the links between the routers, requires two addresses each, so a /30 subnet with the mask 255.255.255.252 is required.

Hint

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.

Hint

Addresses 10.16.10.0 through 10.16.10.63 are taken for the leftmost network. Addresses 10.16.10.192 through 10.16.10.207 are used by the center network.The address space from 208-255 assumes a /28 mask, which does not allow enough host bits to accommodate 25 host addresses.The address ranges that are available include 10.16.10.64/26 and10.16.10.128/26. To accommodate 25 hosts, 5 host bits are needed, so a /27 mask is necessary. Four possible /27 subnets could be created from the available addresses between 10.16.10.64 and 10.16.10.191: 10.16.10.64/27 10.16.10.96/27 10.16.10.128/27 10.16.10.160/27

Hint

IPv6 link-local unicast addresses are in the FE80::/10 prefix range and are not routable. They are used only for communications between devices on the same link.

Hint

In order for a computer to communicate outside its network, it must have a valid default gateway configured.This address cannot be the same as the IP address of the computer.

Hint

There are four basic types of static routes. Floating static routes are backup routes that are placed into the routing table if a primary route is lost. A summary static route aggregates several routes into one, reducing the size of the routing table. Standard static routes are entered manually into the routing table. Default static routes create a gateway of last resort.

Hint

A straight-through cable is commonly used to interconnect a host to a switch and a switch to a router. A crossover cable is used to interconnect similar devices together like switch to a switch, a host to a host, or a router to a router. If a switch has the MDIX capability, a crossover could be used to connect the switch to the router; however, that option is not available. A rollover cable is used to connect to a router or switch console port.

Hint

The administrative distance of 5 added to the end of the static route creates a floating static situation for a static route that goes down. Static routes have a default administrative distance of 1. This route that has an administrative distance of 5 will not be placed into the routing table unless the previously entered static route to the 192.168.10.0/24 goes down or was never entered. The administrative distance of 5 added to the end of the static route configuration creates a floating static route that will be placed in the routing table when the primary route to the same destination network goes down. By default, a static route to the 192.168.10.0/24 network has an administrative distance of 1. Therefore, the floating route with an administrative distance of 5 will not be placed into the routing table unless the previously entered static route to the 192.168.10.0/24 goes down or was never entered. Because the floating route has an administrative distance of 5, the route is preferred to an OSPF-learned route (with the administrative distance of 110) or an EIGRP-learned route (with the administrative distance of 110) to the same destination network.

Hint

The mesh topology provides high availability because every node is connected to all other nodes. Mesh topologies can be found in WANs. A partial mesh topology can also be used where some, but not all, end points connect to one another.

Hint

Carrier sense multiple access collision detection (CSMA/CD) is the access method used with Ethernet. The access method rule of communication dictates how a network device is able to place a signal on the carrier. CSMA/CD dictates those rules on an Ethernet network and CSMA/CA dictates those rules on an 802.11 wireless LAN.

Hint

There are three elements that make up an IPv6 global unicast address. A global routing prefix which is provided by an ISP, a subnet ID which is determined by the organization, and an interface ID which uniquely identifies the interface interface of a host.

Hint

Options matched to the correct selection.

coaxial	UTP	STP
2 conductors	4 pairs of wire without shielding	4 pairs of wire with shielding
used in cable TV	less expensive than similar	used in areas with high electromagnetic activity
shielding acts as the second wire	most commonly used	more difficult to install than similar