642-813 Implementing Cisco IP Switched Networks (SWITCH)

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Question 1

Which of the following specification will allow you to: associate VLAN groups to STP
instances so you can provide multiple forwarding paths for data traffic and enable load

  • A. IEEE 802.1d (STP)
  • B. IEEE 802.1s (MST)
  • C. IEEE 802.1Q (CST)
  • D. IEEE 802.1w (RSTP)

Answer : B

Explanation: IEEE 802.1s MST Overview MST extends the IEEE 802.1w rapid spanning tree (RST) algorithm to multiple spanning trees. This extension provides both rapid convergence and load balancing in a VLAN environment. MST converges faster than PVST+. MST is backward compatible with 802.1D STP, 802.1w (rapid spanning tree protocol [RSTP]), and the Cisco PVST+ architecture. Reference: http://www.cisco.com/en/US/products/hw/switches/ps708/products_configuration_guide_ch apter09186a008007e71a.html#1050594

Question 2

Which statement about the Port Aggregation Protocol is true?

  • A. Configuration changes made on the port-channel interface apply to all physical ports assigned to the port-channel interface.
  • B. Configuration changes made on a physical port that is a member of a port-channel interface apply to the port-channel interface.
  • C. Configuration changes are not permitted with Port Aggregation Protocol. Instead, the standardized Link Aggregation Control Protocol should be used if configuration changes are required.
  • D. The physical port must first be disassociated from the port-channel interface before any configuration changes can be made.

Answer : A

Explanation: The port-channel interface is a logical interface that encompasses the all physical port members of the EtherChannel. So configuration changes made on the port-channel interface apply to all physical ports assigned to the port-channel interface. Reference: http://www.cisco.com/en/US/tech/tk389/tk213/technologies_configuration_example09186a 0080094647.shtml

Question 3

Which statement correctly describes enabling BPDU guard on an access port that is also
enabled for PortFast?

  • A. Upon startup, the port transmits 10 BPDUs. If the port receives a BPDU, PortFast and BPDU guard are disabled on that port and it assumes normal STP operation.
  • B. The access port ignores any received BPDU.
  • C. If the port receives a BPDU, it is placed into the error-disable state.
  • D. BPDU guard is configured only globally and the BPDU filter is required for port-level configuration.

Answer : C

Explanation: When enabled on a port, BPDU Guard shuts down a port that receives a BPDU. When configured globally, BPDU Guard is only effective on ports in the operational PortFast state. In a valid configuration, PortFast Layer 2 LAN interfaces do not receive BPDUs. Reception of a BPDU by a PortFast Layer 2 LAN interface signals an invalid configuration, such as connection of an unauthorized device. BPDU Guard provides a secure response to invalid configurations, because the administrator must manually put the Layer 2 LAN interface back in service. With release 12.1(11b)E, BPDU Guard can also be configured at the interface level. When configured at the interface level, BPDU Guard shuts the port down as soon as the port receives a BPDU, regardless of the PortFast configuration. Reference: http://www.cisco.com/en/US/docs/routers/7600/ios/12.1E/configuration/guide/stp_enha.htm l#wp1020395

Question 4

You have been tasked with configuring multilayer SwitchC, which has a partial
configuration and has been attached to RouterC as shown in the topology diagram.
You need to configure SwitchC so that Hosts H1 arid H2 can successful ping the server S1.
Also SwitchC needs to be able to ping server SI.
Due to administrative restrictions and requirements you should not add/delete vlans or
create trunk links Company policies forbid the use of static or default routing All routes
must be learned via EIGRP 65010 routing protocol.
You do not have access to RouteC, RouterC is correctly configured. No trunking has been
configured on RouterC.
Routed interfaces should use the lowest host on a subnet when possible. The following
subnets are available to implement this solution:
Hosts H1 and H2 are configured with the correct IP address and default gateway.
SwitchC uses Cisco as the enable password.
Routing must only be enabled for the specific subnets shown in the diagram.
Note: Due to administrative restrictions and requirements you should not add or delete
VLANs, changes VLAN port assignments or create trunks. Company policies forbid the use
of static or default routing. All routes must be learning via the EIGRP routing protocol.



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Question 5

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Question 6

Under what circumstances should an administrator prefer local VLANs over end-to-end

  • A. Eighty percent of traffic on the network is destined for Internet sites.
  • B. There are common sets of traffic filtering requirements for workgroups located in multiple buildings.
  • C. Eighty percent of a workgroup’s traffic is to the workgroup’s own local server.
  • D. Users are grouped into VLANs independent of physical location.
  • E. None of the other alternatives apply

Answer : A

Explanation: This geographic location can be as large as an entire building or as small as a single switch inside a wiring closet. In a geographic VLAN structure, it is typical to find 80 percent of the traffic remote to the user (server farms and so on) and 20 percent of the traffic local to the user (local server, printers, and so on). Reference: Building Cisco Multilayer Switched Networks (Cisco Press) page 93

Question 7

Refer to the exhibit.

Which two statements are true? (Choose two.)

  • A. Interface gigabitethernet 0/1 has been configured as Layer 3 ports.
  • B. Interface gigabitethernet 0/1 does not appear in the show vlan output because switchport is enabled.
  • C. Interface gigabitethernet 0/1 does not appear in the show vlan output because it is configured as a trunk interface.
  • D. VLAN2 has been configured as the native VLAN for the 802.1q trunk on interface gigabitethernet 0/1.
  • E. Traffic on VLAN 1 that is sent out gigabitethernet 0/1 will have an 802.1q header applied.
  • F. Traffic on VLAN 2 that is sent out gigabitethernet 0/1 will have an 802.1q header applied.

Answer : C,F

Explanation: From the output of show interface gigabitethernet 0/1 switchport command we can see this port is currently configured as trunked port (Operational Mode: trunk) and uses 802.1q encapsulation. So surely the show vlan command will not list this port -> C is correct. Also from the first output we learned the native VLAN is VLAN 1 (Trunking Native Mode VLAN:1) so only traffic from this VLAN is sent untagged -> traffic sent from VLAN 2 out this port will have an 802.1q header applied -> F is correct.

Question 8

Which statement is true about RSTP topology changes?

  • A. Any change in the state of the port generates a TC BPDU.
  • B. Only non-edge ports moving to the forwarding state generate a TC BPDU.
  • C. If either an edge port or a non-edge port moves to a block state, then a TC BPDU is generated.
  • D. Only edge ports moving to the blocking state generate a TC BPDU.
  • E. Any loss of connectivity generates a TC BPDU.

Answer : B

Explanation: The IEEE 802.1D Spanning Tree Protocol was designed to keep a switched or bridged network loop free, with adjustments made to the network topology dynamically. A topology change typically takes 30 seconds, where a port moves from the Blocking state to the Forwarding state after two intervals of the Forward Delay timer. As technology has improved, 30 seconds has become an unbearable length of time to wait for a production network to failover or "heal" itself during a problem. Topology Changes and RSTP Recall that when an 802.1D switch detects a port state change (either up or down), it signals the Root Bridge by sending topology change notification (TCN) BPDUs. The Root Bridge must then signal a topology change by sending out a TCN message that is relayed to all switches in the STP domain. RSTP detects a topology change only when a non-edge port transitions to the Forwarding state. This might seem odd because a link failure is not used as a trigger. RSTP uses all of its rapid convergence mechanisms to prevent bridging loops from forming. Therefore, topology changes are detected only so that bridging tables can be updated and corrected as hosts appear first on a failed port and then on a different functioning port. When a topology change is detected, a switch must propagate news of the change to other switches in the network so they can correct their bridging tables, too. This process is similar to the convergence and synchronization mechanism-topology change (TC) messages propagate through the network in an ever-expanding wave. Reference: CCNP BCMSN Official Exam Certification Guide, Fourth Edition, Chapter 11: Advanced Spanning Tree Protocol, Rapid Spanning Tree Protocol, Topology Changes and RSTP, p. 269

Question 9

Refer to the exhibit.

Which three statements are true? (Choose three.)

  • A. A trunk link will be formed.
  • B. Only VLANs 1-1001 will travel across the trunk link.
  • C. The native VLAN for switch B is VLAN 1.
  • D. DTP is not running on switch A.
  • E. DTP packets are sent from switch B.

Answer : A,C,E

Explanation: You can manually configure trunk links on Catalyst switches for either ISL or 802.1Q mode. In addition, Cisco has implemented a proprietary, point-to-point protocol called Dynamic Trunking Protocol (DTP) that negotiates a common trunking mode between two switches. The negotiation covers the encapsulation (ISL or 802.1Q) as well as whether the link becomes a trunk at all. You can configure the trunk encapsulation with the switchport trunk encapsulation command, as one of the following: islVLANs are tagged by encapsulating each frame using the Cisco ISL protocol. dot1qVLANs are tagged in each frame using the IEEE 802.1Q standard protocol. The only exception is the native VLAN, which is sent normally and not tagged at all. negotiate (the default)The encapsulation is negotiated to select either ISL or IEEE 802.1Q, whichever is supported by both ends of the trunk. If both ends support both types, ISL is favored. (The Catalyst 2950 switch does not support ISL encapsulation.) In the switchport mode command, you can set the trunking mode to any of the following: trunkThis setting places the port in permanent trunking mode. The corresponding switch port at the other end of the trunk should be similarly configured because negotiation is not allowed. You should also manually configure the encapsulation mode. dynamic desirable (the default)The port actively attempts to convert the link into trunking mode. If the far-end switch port is configured to trunk, dynamic desirable, or dynamic auto mode, trunking is successfully negotiated. dynamic autoThe port converts the link into trunking mode. If the far-end switch port is configured to trunk or dynamic desirable, trunking is negotiated. Because of the passive negotiation behavior, the link never becomes a trunk if both ends of the link are left to the dynamic auto default. Reference: http://www.cisco.com/en/US/docs/switches/lan/catalyst3560/software/release/12.2_25_se/c onfiguration/guide/swvlan.html#wp1100014

Question 10

On a multilayer Cisco Catalyst switch, which interface command is used to convert a Layer
3 interface to a Layer 2 interface?

  • A. switchport
  • B. no switchport
  • C. switchport mode access
  • D. switchport access vlan vlan-id

Answer : A

Explanation: The switchport command puts the port in Layer 2 mode. Then, you can use other switchport command keywords to configure trunking, access VLANs, and so on. Reference: http://www.cisco.com/en/US/docs/switches/lan/catalyst3560/software/release/12.2_25_se/c onfiguration/guide/swint.html#wp1415008

Question 11

Refer to the exhibit.

All network links are FastEthernet. Although there is complete connectivity throughout the
network, Front Line users report that they experience slower network performance when
accessing the server farm than the Reception office experiences. Which two statements
are true? (Choose two.)

  • A. Changing the bridge priority of S1 to 4096 would improve network performance.
  • B. Changing the bridge priority of S1 to 36864 would improve network performance.
  • C. Changing the bridge priority of S2 to 36864 would improve network performance.
  • D. Changing the bridge priority of S3 to 4096 would improve network performance.
  • E. Disabling the Spanning Tree Protocol would improve network performance.
  • F. Upgrading the link between S2 and S3 to Gigabit Ethernet would improve performance.

Answer : B,D

Explanation: All three switches have the same bridge priority (32768 default value) and S1 has the lowest MAC -> S1 is the root bridge and all traffic must go through it -> Front Line Users (S2) must go through S1 to reach Server Farm (S3). To overcome this problem, S2 or S3 should become the root switch and we can do it by changing the bridge priority of S1 to a higher value or lower the bridge priority value Reference: CCNP Self-Study CCNP BCMSN Official Exam Certification Guide, Fourth Edition, Chapter 9: Spanning Tree Configuration, STP Root Bridge, p. 219.

Question 12

Refer to the exhibit.

Both host stations are part of the same subnet but are in different VLANs. On the basis of
the information presented in the exhibit, which statement is true about an attempt to ping
from host to host?

  • A. A trunk port will need to be configured on the link between Sw_A and Sw_B for the ping command to be successful.
  • B. The two different hosts will need to be in the same VLAN in order for the ping command to be successful.
  • C. A Layer 3 device is needed for the ping command to be successful.
  • D. The ping command will be successful without any further configuration changes.

Answer : D

Explanation: For two hosts in different VLANs, we must use a layer 3 device to transport packages between them. However, in this case both switches are set in access mode therefore the VLAN information sent between them will be set as untagged. Moreover, they are in the same subnet so they can ping each other without a layer 3 device.

Question 13

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Question 14

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Question 15

By default, which statement is correct when an IEEE 802.1Q trunk port receives an
untagged frame?

  • A. The frame is considered in the native VLAN and forwarded to the ports associated with that VLAN.
  • B. The frame is encapsulated and tagged as in the native VLAN.
  • C. The frame is broadcast on all ports regardless of VLAN association.
  • D. The frame is dropped.

Answer : A

Explanation: If a switch receives untagged frames on a trunk port, they are assumed to be part of the VLAN that are designated on the switchport as the native VLAN.

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