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QUESTION 21
Which two benefits are provided by creating VLANs? (Choose two.)

A.    added security
B.    dedicated bandwidth
C.    provides segmentation
D.    allows switches to route traffic between subinterfaces
E.    contains collisions

Answer: AC
Explanation:
A VLAN is a switched network that is logically segmented on an organizational basis, by functions, project teams, or applications rather than on a physical or geographical basis.
Security:
VLANs also improve security by isolating groups. High-security users can be grouped into a VLAN, possible on the same physical segment, and no users outside that VLAN can communicate with them
LAN Segmentation
VLANs allow logical network topologies to overlay the physical switched infrastructure such that any arbitrary collection of LAN ports can be combined into an autonomous user group or community of interest. The technology logically segments the network into separate Layer 2 broadcast domains whereby packets are switched between ports designated to be within the same VLAN. By containing traffic originating on a particular LAN only to other LANs in the same VLAN, switched virtual networks avoid wasting bandwidth.

QUESTION 22
Which command can be used from a PC to verify the connectivity between hosts that connect through a switch in the same LAN?

A.    pingaddress
B.    tracertaddress
C.    tracerouteaddress
D.    arpaddress

Answer: A
Explanation:
ICMP pings are used to verify connectivity between two IP hosts. Traceroute is used to verify the router hop path traffic will take but in this case since the hosts are in the same LAN there will be no router hops involved.

QUESTION 23
Which two of these are characteristics of the 802.1Q protocol? (Choose two.)

A.    It is used exclusively for tagging VLAN frames and does not address network reconvergence following
switched network topology changes.
B.    It modifies the 802.3 frame header, and thus requires that the FCS be recomputed.
C.    It is a Layer 2 messaging protocol which maintains VLAN configurations across networks.
D.    It includes an 8-bit field which specifies the priority of a frame.
E.    It is a trunking protocol capable of carrying untagged frames.

Answer: BE
Explanation:
802.1Q protocol, or Virtual Bridged Local Area Networks protocol, mainly stipulates the realization of the VLAN. 802.1Q is a standardized relay method that inserts 4 bytes field into the original Ethernet frame and re-calculate the FCS. 802.1Q frame relay supports two types of frame: marked and non-marked. Non-marked frame carries no VLAN identification information.

QUESTION 24
Refer to the exhibit. Each of these four switches has been configured with a hostname, as well as being configured to run RSTP. No other configuration changes have been made. Which three of these show the correct RSTP port roles for the indicated switches and interfaces? (Choose three.)

A.    SwitchA, Fa0/2, designated
B.    SwitchA, Fa0/1, root
C.    SwitchB, Gi0/2, root
D.    SwitchB, Gi0/1, designated
E.    SwitchC, Fa0/2, root
F.    SwitchD, Gi0/2, root

Answer: ABF
Explanation:
The question says “no other configuration changes have been made” so we can understand these switches have the same bridge priority. Switch C has lowest MAC address so it will become root bridge and 2 of its ports (Fa0/1 & Fa0/2) will be designated ports. Because SwitchC is the root bridge so the 2 ports nearest SwitchC on SwitchA (Fa0/1) and SwitchD (Gi0/2) will be root ports..
Now we come to the most difficult part of this question: SwitchB must have a root port so which port will it choose? To answer this question we need to know about STP cost and port cost. In general, “cost” is calculated based on bandwidth of the link. The higher the bandwidth on a link, the lower the value of its cost. Below are the cost values you should memorize:

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SwitchB will choose the interface with lower cost to the root bridge as the root port so we must calculate the cost on interface Gi0/1 & Gi0/2 of SwitchB to the root bridge. This can be calculated from the “cost to the root bridge” of each switch because a switch always advertises its cost to the root bridge in its BPDU. The receiving switch will add its local port cost value to the cost in the BPDU.
One more thing to notice is that a root bridge always advertises the cost to the root bridge (itself) with an initial value of 0.
Now let’s have a look at the topology again

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SwitchC advertises its cost to the root bridge with a value of 0. Switch D adds 4 (the cost value of 1Gbps link) and advertises this value (4) to SwitchB. SwitchB adds another 4 and learns that it can reach SwitchC via Gi0/1 port with a total cost of 8. The same process happens for SwitchA and SwitchB learns that it can reach SwitchC via Gi0/2 with a total cost of 23 -> Switch B chooses Gi0/1 as its root port ->
Now our last task is to identify the port roles of the ports between SwitchA & SwitchB. It is rather easy as the MAC address of SwitchA is lower than that of SwitchB so Fa0/2 of SwitchA will be designated port while Gi0/2 of SwitchB will be alternative port.
Below summaries all the port roles of these switches:

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+ DP: Designated Port (forwarding state)
+ RP: Root Port (forwarding state)

QUESTION 25
What is one benefit of PVST+?

A.    PVST+ supports Layer 3 load balancing without loops.
B.    PVST+ reduces the CPU cycles for all the switches in the network.
C.    PVST+ allows the root switch location to be optimized per VLAN.
D.    PVST+ automatically selects the root bridge location, to provide optimized bandwidth usage.

Answer: C
Explanation:
The PVST+ provides Layer 2 load-balancing for the VLAN on which it runs. You can create different logical topologies by using the VLANs on your network to ensure that all of your links are used but that no one link is oversubscribed. Each instance of PVST+ on a VLAN has a single root switch. This root switch propagates the spanning-tree information associated with that VLAN to all other switches in the network. Because each switch has the same information about the network, this process ensures that the network topology is maintained and optimized per VLAN.
Reference:
http://www.cisco.com/en/US/docs/switches/lan/catalyst3750x_3560x/software/release/12.2_55_se /configuration/guide/swstp.html

QUESTION 26
Which are valid modes for a switch port used as a VLAN trunk? (Choose three.)

A.    transparent
B.    auto
C.    on
D.    desirable
E.    blocking
F.    forwarding

Answer: BCD

QUESTION 27
Which three of these statements regarding 802.1Q trunking are correct? (Choose three.)

A.    802.1Q native VLAN frames are untagged by default.
B.    802.1Q trunking ports can also be secure ports.
C.    802.1Q trunks can use 10 Mb/s Ethernet interfaces.
D.    802.1Q trunks require full-duplex, point-to-point connectivity.
E.    802.1Q trunks should have native VLANs that are the same at both ends.

Answer: ACE
Explanation:
By default, 802.1Q trunk defined Native VLAN in order to forward unmarked frame. Switches can forward Layer 2 frame from Native VLAN on unmarked trunks port. Receiver switches will transmit all unmarked packets to Native VLAN. Native VLAN is the default VLAN configuration of port. Note for the 802.1Q trunk ports between two devices, the same Native VLAN configuration is required on both sides of the link. If the Native VLAN in 802.1Q trunk ports on same trunk link is properly configured, it could lead to layer 2 loops. The 802.1Q trunk link transmits VLAN information through Ethernet.

QUESTION 28
Which term describes a spanning-tree network that has all switch ports in either the blocking or fowarding state?

A.    converged
B.    redundant
C.    provisioned
D.    spanned

Answer: A
Explanation:
Spanning Tree Protocol convergence (Layer 2 convergence) happens when bridges and switches have transitioned to either the forwarding or blocking state. When layer 2 is converged, root bridge is elected and all port roles (Root, Designated and Non-Designated) in all switches are selected.

QUESTION 29
What are the possible trunking modes for a switch port? (Choose three.)

A.    transparent
B.    auto
C.    on
D.    desirable
E.    client
F.    forwarding

Answer: BCD

QUESTION 30
Which two of these statements regarding RSTP are correct? (Choose two.)

A.    RSTP cannot operate with PVST+.
B.    RSTP defines new port roles.
C.    RSTP defines no new port states.
D.    RSTP is a proprietary implementation of IEEE 802.1D STP.
E.    RSTP is compatible with the original IEEE 802.1D STP.

Answer: BE
Explanation:
When network topology changes, rapid spanning tree protocol (IEEE802.1W, referred to as RSTP) will speed up significantly the speed to re-calculate spanning tree. RSTP not only defines the role of other ports: alternative port and backup port, but also defines status of 3 ports: discarding status, learning status, forwarding status.
RSTP is 802.1D standard evolution, not revolution. It retains most of the parameters, and makes no changes.

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QUESTION 11
Which two commands can be used to verify a trunk link configuration status on a given Cisco switch interface? (Choose two.)

A.    show interface trunk
B.    show interface interface
C.    show ip interface brief
D.    show interface vlan
E.    show interface switchport

Answer: AE

QUESTION 12
Which command enables RSTP on a switch?

A.    spanning-tree uplinkfast
B.    spanning-tree mode rapid-pvst
C.    spanning-tree backbonefast
D.    spanning-tree mode mst

Answer: B
Explanation:
Ethernet network is a shared environment so all devices have the right to access to the medium. If more than one device transmits simultaneously, the signals collide and can not reach the destination.
If a device detects another device is sending, it will wait for a specified amount of time before attempting to transmit.
When there is no traffic detected, a device will transmit its message. While this transmission is occurring, the device continues to listen for traffic or collisions on the LAN. After the message is sent, the device returns to its default listening mode.

QUESTION 13
What is the function of the command switchport trunk native vlan 999 on a Cisco Catalyst switch?

A.    It creates a VLAN 999 interface.
B.    It designates VLAN 999 for untagged traffic.
C.    It blocks VLAN 999 traffic from passing on the trunk.
D.    It designates VLAN 999 as the default for all unknown tagged traffic.

Answer: B
Explanation:
Configuring the Native VLAN for Untagged Traffic
A trunk port configured with 802.1Q tagging can receive both tagged and untagged traffic. By default, the switch forwards untagged traffic in the native VLAN configured for the port. The native VLAN is VLAN 1 by default.

QUESTION 14
Why will a switch never learn a broadcast address?

A.    Broadcasts only use network layer addressing.
B.    A broadcast frame is never forwarded by a switch.
C.    A broadcast address will never be the source address of a frame.
D.    Broadcast addresses use an incorrect format for the switching table.
E.    Broadcast frames are never sent to switches.

Answer: C
Explanation:
Switches dynamically learn MAC addresses based on the source MAC addresses that it sees, and since a broadcast is never the source, it will never learn the broadcast address.

QUESTION 15
Which two link protocols are used to carry multiple VLANs over a single link? (Choose two.)

A.    VTP
B.    802.1q
C.    IGP
D.    ISL
E.    802.3u

Answer: BD
Explanation:
Cisco switches can use two different encapsulation types for trunks, the industry standard 802.1q or the Cisco proprietary ISL. Generally, most network engineers prefer to use 802.1q since it is standards based and will interoperate with other vendors.

QUESTION 16
Assuming the default switch configuration, which VLAN range can be added, modified, and removed on a Cisco switch?

A.    1 through 1001
B.    2 through 1001
C.    1 through 1002
D.    2 through 1005

Answer: B
Explanation:
VLAN 1 is the default VLAN on Cisco switch. It always exists and can not be added, modified or removed.
VLANs 1002-1005 are default VLANs for FDDI & Token Ring and they can’t be deleted or used for Ethernet.

QUESTION 17
Which statement about VLAN operation on Cisco Catalyst switches is true?

A.    When a packet is received from an 802.1Q trunk, the VLAN ID can be determined from the source
MAC address and the MAC address table.
B.    Unknown unicast frames are retransmitted only to the ports that belong to the same VLAN.
C.    Broadcast and multicast frames are retransmitted to ports that are configured on different VLAN.
D.    Ports between switches should be configured in access mode so that VLANs can span across the ports.

Answer: B
Explanation:
Each VLAN resides in its own broadcast domain, so incoming frames with unknown destinations are only transmitted to ports that reside in the same VLAN as the incoming frame.

QUESTION 18
Which three statements about RSTP are true? (Choose three.)

A.    RSTP significantly reduces topology reconverging time after a link failure.
B.    RSTP expands the STP port roles by adding the alternate and backup roles.
C.    RSTP port states are blocking, discarding, learning, or forwarding.
D.    RSTP provides a faster transition to the forwarding state on point-to-point links than STP does.
E.    RSTP also uses the STP proposal-agreement sequence.
F.    RSTP uses the same timer-based process as STP on point-to-point links.

Answer: ABD
Explanation:
One big disadvantage of STP is the low convergence which is very important in switched network. To overcome this problem, in 2001, the IEEE with document 802.1w introduced an evolution of the Spanning Tree Protocol: Rapid Spanning Tree Protocol (RSTP), which significantly reduces the convergence time after a topology change occurs in the network. While STP can take 30 to 50 seconds to transit from a blocking state to a forwarding state, RSTP is typically able to respond less than 10 seconds of a physical link failure.
RSTP works by adding an alternative port and a backup port compared to STP. These ports are allowed to immediately enter the forwarding state rather than passively wait for the network to converge.
RSTP bridge port roles:
* Root port – A forwarding port that is the closest to the root bridge in terms of path cost
* Designated port – A forwarding port for every LAN segment
* Alternate port – A best alternate path to the root bridge. This path is different than using the root port. The alternative port moves to the forwarding state if there is a failure on the designated port for the segment.
* Backup port – A backup/redundant path to a segment where another bridge port already connects. The backup port applies only when a single switch has two links to the same segment (collision domain). To have two links to the same collision domain, the switch must be attached to a hub.
* Disabled port – Not strictly part of STP, a network administrator can manually disable a port

QUESTION 19
At which layer of the OSI model is RSTP used to prevent loops?

A.    physical
B.    data link
C.    network
D.    transport

Answer: B
Explanation:
RSTP and STP operate on switches and are based on the exchange of Bridge Protocol Data Units (BPDUs) between switches. One of the most important fields in BPDUs is the Bridge Priority in which the MAC address is used to elect the Root Bridge -> RSTP operates at Layer 2 ?Data Link layer -> .

QUESTION 20
What does a Layer 2 switch use to decide where to forward a received frame?

A.    source MAC address
B.    source IP address
C.    source switch port
D.    destination IP address
E.    destination port address
F.    destination MAC address

Answer: F
Explanation:
When a frame is received, the switch looks at the destination hardware address and finds the interface if it is in its MAC address table. If the address is unknown, the frame is broadcast on all interfaces except the one it was received on.

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QUESTION 1
Which layer in the OSI reference model is responsible for determining the availability of the receiving program and checking to see if enough resources exist for that communication?

A.    transport
B.    network
C.    presentation
D.    session
E.    application

Answer: E
Explanation:
This question is to examine the OSI reference model. The Application layer is responsible for identifying and establishing the availability of the intended communication partner and determining whether sufficient resources for the intended communication exist.

QUESTION 2
Which of the following describes the roles of devices in a WAN? (Choose three.)

A.    A CSU/DSU terminates a digital local loop.
B.    A modem terminates a digital local loop.
C.    A CSU/DSU terminates an analog local loop.
D.    A modem terminates an analog local loop.
E.    A router is commonly considered a DTE device.
F.    A router is commonly considered a DCE device.

Answer: ADE
Explanation:
The idea behind a WAN is to be able to connect two DTE networks together through a DCE network. The network’s DCE device (includes CSU/DSU) provides clocking to the DTE-connected interface (the router’s serial interface).
A modem modulates outgoing digital signals from a computer or other digital device to analog signals for a conventional copper twisted pair telephone line and demodulates the incoming analog signal and converts it to a digital signal for the digital device. A CSU/DSU is used between two digital lines –
For more explanation of answer D, in telephony the local loop (also referred to as a subscriber line) is the physical link or circuit that connects from the demarcation point of the customer premises to the edge of the carrier or telecommunications service provider’s network. Therefore a modem terminates an analog local loop is correct.

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QUESTION 3
A network administrator is verifying the configuration of a newly installed host by establishing an FTP connection to a remote server. What is the highest layer of the protocol stack that the network administrator is using for this operation?

A.    application
B.    presentation
C.    session
D.    transport
E.    internet
F.    data link

Answer: A
Explanation:
FTP belongs to Application layer and it is also the highest layer of the OSI model.

QUESTION 4
A network interface port has collision detection and carrier sensing enabled on a shared twisted pair network. From this statement, what is known about the network interface port?

A.    This is a 10 Mb/s switch port.
B.    This is a 100 Mb/s switch port.
C.    This is an Ethernet port operating at half duplex.
D.    This is an Ethernet port operating at full duplex.
E.    This is a port on a network interface card in a PC.

Answer: C
Explanation:
Modern Ethernet networks built with switches and full-duplex connections no longer utilize CSMA/CD. CSMA/CD is only used in obsolete shared media Ethernet (which uses repeater or hub).

QUESTION 5
A receiving host computes the checksum on a frame and determines that the frame is damaged. The frame is then discarded. At which OSI layer did this happen?

A.    session
B.    transport
C.    network
D.    data link
E.    physical

Answer: D
Explanation:
The Data Link layer provides the physical transmission of the data and handles error notification, network topology, and flow control. The Data Link layer formats the message into pieces, each called a data frame, and adds a customized header containing the hardware destination and source address. Protocols Data Unit (PDU) on Datalink layer is called frame. According to this question the frame is damaged and discarded which will happen at the Data Link layer.

QUESTION 6
Which of the following correctly describe steps in the OSI data encapsulation process? (Choose two.)

A.    The transport layer divides a data stream into segments and may add reliability and flow control information.
B.    The data link layer adds physical source and destination addresses and an FCS to the segment.
C.    Packets are created when the network layer encapsulates a frame with source and destination host
addresses and protocol-related control information.
D.    Packets are created when the network layer adds Layer 3 addresses and control information to a segment.
E.    The presentation layer translates bits into voltages for transmission across the physical link.

Answer: AD
Explanation:
The Application Layer (Layer 7) refers to communications services to applications and is the interface between the network and the application. Examples include. Telnet, HTTP, FTP, Internet browsers, NFS, SMTP gateways, SNMP, X.400 mail, and FTAM.
The Presentation Layer (Layer 6) defining data formats, such as ASCII text, EBCDIC text, binary, BCD, and JPEG. Encryption also is defined as a presentation layer service. Examples include. JPEG, ASCII, EBCDIC, TIFF, GIF, PICT, encryption, MPEG, and MIDI.
The Session Layer (Layer 5) defines how to start, control, and end communication sessions. This includes the control and management of multiple bidirectional messages so that the application can be notified if only some of a series of messages are completed. This allows the presentation layer to have a seamless view of an incoming stream of data. The presentation layer can be presented with data if all flows occur in some cases. Examples include. RPC, SQL, NFS, NetBios names, AppleTalk ASP, and DECnet SCP
The Transport Layer (Layer 4) defines several functions, including the choice of protocols. The most important Layer 4 functions are error recovery and flow control. The transport layer may provide for retransmission, i.e., error recovery, and may use flow control to prevent unnecessary congestion by attempting to send data at a rate that the network can accommodate, or it might not, depending on the choice of protocols. Multiplexing of incoming data for different flows to applications on the same host is also performed. Reordering of the incoming data stream when packets arrive out of order is included. Examples include. TCP, UDP, and SPX.
The Network Layer (Layer 3) defines end-to-end delivery of packets and defines logical addressing to accomplish this. It also defines how routing works and how routes are learned; and how to fragment a packet into smaller packets to accommodate media with smaller maximum transmission unit sizes. Examples include. IP, IPX, AppleTalk DDP, and ICMP. Both IP and IPX define logical addressing, routing, the learning of routing information, and end-to-end delivery rules. The IP and IPX protocols most closely match the OSI network layer (Layer 3) and are called Layer 3 protocols because their functions most closely match OSI’s Layer 3.
The Data Link Layer (Layer 2) is concerned with getting data across one particular link or medium.
The data link protocols define delivery across an individual link. These protocols are necessarily concerned with the type of media in use. Examples includE. IEEE 802.3/802.2, HDLC, Frame Relay, PPP, FDDI, ATM, and IEEE 802.5/802.2.

QUESTION 7
Which three statements accurately describe Layer 2 Ethernet switches? (Choose three.)

A.    Spanning Tree Protocol allows switches to automatically share VLAN information.
B.    Establishing VLANs increases the number of broadcast domains.
C.    Switches that are configured with VLANs make forwarding decisions based on both Layer 2 and
Layer 3 address information.
D.    Microsegmentation decreases the number of collisions on the network.
E.    In a properly functioning network with redundant switched paths, each switched segment will contain
one root bridge with all its ports in the forwarding state. All other switches in that broadcast domain will
have only one root port.
F.    If a switch receives a frame for an unknown destination, it uses ARP to resolve the address.

Answer: BDE
Explanation:
Microsegmentation is a network design (functionality) where each workstation or device on a network gets its own dedicated segment (collision domain) to the switch. Each network device gets the full bandwidth of the segment and does not have to share the segment with other devices. Microsegmentation reduces and can even eliminate collisions because each segment is its own collision domain -> .
Note: Microsegmentation decreases the number of collisions but it increases the number of collision domains.

QUESTION 8
Where does routing occur within the DoD TCP/IP reference model?

A.    application
B.    internet
C.    network
D.    transport

Answer: B
Explanation:
The picture below shows the comparison between TCP/IP model & OSI model. Notice that the Internet Layer of TCP/IP is equivalent to the Network Layer which is responsible for routing decision.

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QUESTION 9
Refer to exhibit: Which destination addresses will be used by Host A to send data to Host C? (Choose two.)

A.    the IP address of Switch 1
B.    the MAC address of Switch 1
C.    the IP address of Host C
D.    the MAC address of Host C
E.    the IP address of the router’s E0 interface
F.    the MAC address of the router’s E0 interface

Answer: CF
Explanation:
While transferring data through many different networks, the source and destination IP addresses are not changed. Only the source and destination MAC addresses are changed. So in this case Host A will use the IP address of Host C and the MAC address of E0 interface to send data. When the router receives this data, it replaces the source MAC address with it own E1 interface’s MAC address and replaces the destination MAC address with Host C’s MAC address before sending to Host C .

QUESTION 10
For what two purposes does the Ethernet protocol use physical addresses? (Choose two.)

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A.    to uniquely identify devices at Layer 2
B.    to allow communication with devices on a different network
C.    to differentiate a Layer 2 frame from a Layer 3 packet
D.    to establish a priority system to determine which device gets to transmit first
E.    to allow communication between different devices on the same network
F.    to allow detection of a remote device when its physical address is unknown

Answer: AE
Explanation:
Physical addresses or MAC addresses are used to identify devices at layer 2.
MAC addresses are only used to communicate on the same network. To communicate on different network we have to use Layer 3 addresses (IP addresses) -> B is not correct.
Layer 2 frame and Layer 3 packet can be recognized via headers. Layer 3 packet also contains physical address ->
On Ethernet, each frame has the same priority to transmit by default -> All devices need a physical address to identify itself. If not, they can not communicate –>

 

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QUESTION 101
Refer to the exhibit. The Lakeside Company has the internetwork in the exhibit. The administrator would like to reduce the size of the routing table on the Central router. Which partial routing table entry in the Central router represents a route summary that represents the LANs in Phoenix but no additional subnets?

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