Testking_640-802_V13

Why would the TestKing administrator change the value of the spanning-tree priority of a switch?

A.in order to optimize the path that frames take from source to destination

B.to increase the priority so a designated port will become a root port

C.to increase the BID, so the switch is more likely to become root bridge

D.in order to allow VLANs to be sent from one switch to another across a single link

E.to force a given switch to become an STP server

F.None of the above

Answer: A Explanation:

The Bridge Priority is used to measure the preference of a bridge in the spanning-tree Algorithm. The possible values range between 0 and 65,535. The default setting is 32,768. By adjusting the priority, the root bridge can be manually assigned to meet the needs of the network administrator.

QUESTION NO: 31

What value is primarily used to determine which port becomes the root port on each nonroot switch in a spanning-tree topology?

A.path cost

B.lowest port MAC address

C.VTP revision number

D.highest port priority number

E.port priority number and MAC address

F.None of the above

Answer: A Explanation:

At the conclusion of the root bridge election process, the switches move on to selecting Root Ports. The Root Port of a bridge is the port that is closest to the Root Bridge in terms of Path Cost. Every non-Root Bridge must select one Root Port. Again, bridges use the concept of cost to measure closeness. As with some routing metrics, the measure of closeness using STP is not necessarily reflected by hop count. Specifically, bridges track what is referred to as Root Path Cost, which is the cumulative cost of all links to the Root Bridge.

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QUESTION NO: 32

Refer to the topology shown in the exhibit below:

Based on the information above, which ports will be STP designated ports if all the links are operating at the same bandwidth? (Choose three)

A.Switch A - Fa0/1

B.Switch B - Fa0/0

C.Switch A - Fa0/0

D.Switch B - Fa0/1

E.Switch C - Fa0/0

F.Switch C - Fa0/1

Answer: A, B, D Explanation:

To remove the possibility of bridging loops, STP makes a final computation to identify one Designated Port on each network segment. Suppose that two or more switches have ports connected to a single common network segment. If a frame appears on that segment, all the bridges attempt to forward it to its destination. Recall that this behavior was the basis of a bridging loop and should be avoided.

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Instead, only one of the links on a segment should forward traffic to and from that segment-the one that is selected as the Designated Port. Switches choose a Designated Port based on the lowest cumulative Root Path Cost to the Root Bridge. For example, a switch always has an idea of its own Root Path Cost, which it announces in its own BPDUs. If a neighboring switch on a shared LAN segment sends a BPDU announcing a lower Root Path Cost, the neighbor must have the Designated Port. If a switch learns only of higher Root Path Costs from other BPDUs received on a port, however, it then correctly assumes that its own receiving port is the Designated Port for the segment. Notice that the entire STP determination process has served only to identify bridges and ports. All ports are still active, and bridging loops still might lurk in the network. STP has a set of progressive states that each port must go through, regardless of the type or identification. These states actively prevent loops from forming and are described in the next section.

Note:

In each determination process discussed so far, two or more links might have identical Root Path Costs. This results in a tie condition, unless other factors are considered. All tie-breaking STP decisions are based on the following sequence of four conditions:

1.Lowest Root Bridge ID

2.Lowest Root Path Cost to Root Bridge

3.Lowest Sender Bridge ID

4.Lowest Sender Port ID

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The three switches have chosen their Designated Ports (DP) for the following reasons:

1.Catalyst A- Because this switch is the Root Bridge, all its active ports are Designated Ports, by definition. At the Root Bridge, the Root Path Cost of each port is 0.

2.Catalyst B- Catalyst A port 1/1 is the DP for the Segment A-B because it has the lowest Root Path Cost (0). Catalyst B port 1/2 is the DP for segment B-C. The Root Path Cost for each end of this segment is 19, determined from the incoming BPDU on port 1/1. Because the Root Path Cost is equal on both ports of the segment, the DP must be chosen by the next criteria-the lowest Sender Bridge ID. When Catalyst B sends a BPDU to Catalyst C, it has the lowest MAC address in the Bridge ID. Catalyst C also sends a BPDU to Catalyst B, but its Sender Bridge ID is higher. Therefore, Catalyst B port 1/2 is selected as the segment's DP.

3.Catalyst C- Catalyst A port 1/2 is the DP for Segment A-C because it has the lowest

Root Path Cost (0). Catalyst B port 1/2 is the DP for Segment B-C. Therefore, Catalyst C port 1/2 will be neither a Root Port nor a Designated Port. As discussed in the next

section, any port that is not elected to either position enters the Blocking state. Where blocking occurs, bridging loops are broken.

Reference: CCNP BCMSN Exam Certification Guide, 3rd Edition, Cisco Press

QUESTION NO: 33

Exhibit:

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The switches in the exhibit above are configured with the default parameters. What can be determined from the exhibit?

A.Fa0/2 on SW-1 and Fa0/2 on SW-2 are nondesignated ports.

B.SW-1 is the backup designated root bridge.

C.SW-3 is the root bridge.

D.Fa0/3 on SW-1 and Fa0/3 on SW-2 are attached to the lowest-cost paths to the root bridge.

E.None of the above

Answer: C Explanation:

Remember that one root switch is identified per-VLAN. After the root switch identification, the switches adhere to these rules:

1. STP Rule 1-All ports of the root switch must be in forwarding mode.

Next, each switch determines the best path to get to the root. The switches determine this path by a comparison of the information in all the BPDUs that the switches receive on all ports. The switch uses the port with the least amount of information in the BPDU in order to get to the root switch; the port with the least amount of information in the BPDU is the root port. After a switch determines the root port, the switch proceeds to rule 2.

1. STP Rule 2-The root port must be set to forwarding mode.

In addition, the switches on each LAN segment communicate with each other to determine which switch is best to use in order to move data from that segment to the root bridge. This switch is called the designated switch.

1. STP Rule 3

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-In a single LAN segment, the port of the designated switch that connects to that LAN segment must be placed in forwarding mode.

2. STP Rule 4-All the other ports in all the switches (VLAN-specific) must be placed in blocking mode. The rule only applies to ports that connect to other bridges or switches. STP does not affect ports that connect to workstations or PCs. These ports remain forwarded.

Our answer can be found in Rule 1 above. Since none of the ports in SW-3 are blocking, we can determine that this switch must be the root.

Reference: http://www.cisco.com/en/US/tech/tk389/tk621/technologies_configuration_example09186a008009467c.shtm

QUESTION NO: 34

In the TestKing switched LAN environment, what does the IEEE 802.1Q standard describe?

A.VLAN pruning

B.A method of VLAN trunking

C.An approach to wireless LAN communication

D.The operation of VTP

E.The process for root bridge selection

F.None of the above

Answer: B Explanation:

A broadcast domain must sometimes exist on more than one switch in the network. To accomplish this, one switch must send frames to another switch and indicate which VLAN a particular frame belongs to. On Cisco switches, a trunk link is created to accomplish this VLAN identification. ISL and IEEE 802.1Q are different methods of putting a VLAN identifier in a Layer 2 frame.

The IEEE 802.1Q protocol interconnects VLANs between multiple switches, routers, and servers. With 802.1Q, a network administrator can define a VLAN topology to span multiple physical devices.

Cisco switches support IEEE 802.1Q for FastEthernet and Gigabit Ethernet interfaces. An 802.1Q trunk link provides VLAN identification by adding a 4-byte tag to an Ethernet Frame as it leaves a trunk port.

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QUESTION NO: 35

You are an administrator of the TestKing switched network and your goal is to reduce some of the administrative overhead on your network. You plan on achieving this by configuring a new VLAN for each department in the TestKing network. However, you need to share the VLAN information across numerous switches. Which of the following would allow you accomplish this?

A.STP

B.GVRP

C.SNMP

D.VTP

E.DHCP

F.None of the above

Answer: D Explanation:

The VTP (VLAN Trunking Protocol) is a Cisco Layer 2 messaging protocol that manages the addition, deletion, and renaming of VLANs on a network-wide basis. It allows for VLAN information to span multiple switches within the switch domain.

Incorrect Answers:

A.STP is a switching protocol but it is used for preventing network loops.

B.GVARP is an actual protocol used in switch administration, but it beyond the scope of what a CCNA is expected to know.

C.SNMP is a protocol used for managing and monitoring networks

E. DHCP is the Dynamic Host Configuration Protocol, which allows for PC's to obtain their IP address dynamically upon booting up, along with their DNS and default gateway information.

Section 9: Describe how VLANs create logically separate networks and the need for routing between them (10 questions)

QUESTION NO: 1

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Which of the following a true statements regarding the use of VLANs to segment a network? (Select three)

A.They increase the size of collision domains

B.They allow logical grouping of users by function.

C.They can enhance network security.

D.They increase the size of the broadcast domain while decreasing the number of collision domains.

E.They increase the number of broadcast domains while decreasing the size of the broadcast domains.

F.They simplify switch administration.

Answer: B, C, E Explanation:

VLANs are used to segment a LAN into multiple, smaller LANs. This can be used to enhance security as local traffic from one VLAN will not be passed to users in other VLANS.

Incorrect Answers:

A. VLANs are used to decrease the size of a collision domain, not increase it. D. The opposite is true.

F. The default operation of a switch is to allow all traffic and to enable all ports in VLAN 1. The use of VLANs will increase the complexity of the switch environment, making for more difficult administration.

QUESTION NO: 2

You wish to segment your LAN into multiple broadcast domains. Which technology method should you implement in order to do this?

A.Transparent bridging

B.Cut-through switching

C.Fragment-free switches

D.Virtual LANs

E.Store-and-forward switching

F.None of the above

Answer: D

Explanation:

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The creation of VLANs in a switch will provide separate Broadcast domains. By default, all ports in a Catalyst switch belong to VLAN 1. By creating additional VLANs, the LAN will be logically segmented into separate broadcast domains.

Incorrect Answers

A. Transparent bridging is called Transparent because the endpoints devices do not need to know that the bridges exists. It will not play any role for creating separate broadcast domain

B, E. Both of these are switching methods.

C. This has nothing to do with the creation of multiple broadcast domains.

QUESTION NO: 3

TestKing has implemented the use of VLANs in their network. Which of the following are considered to be a benefit of VLANs? (Choose three)

A.They increase the size of collision domains.

B.They allow logical grouping of users by function.

C.They can enhance network security,

D.The increase the size of broadcast domains while decreasing the number of the broadcast domains.

E.The increase the number of broadcast domains while decreasing the size of the broadcast domains.

F.They simplify switch administration.

Answer: B, C, E

Explanation:

There are many motivations for using VLANs, including these:

1.To group users by department, or by groups that work together, instead of by physical location. (B)

2.To reduce overhead by limiting the size of each broadcast domain (E)

3.To enforce better security by keeping sensitive devices on a separate VLAN (C)

4.To separate specialized traffic from mainstream traffic - for example, putting IP telephones on a separate VLAN form user PCs.

QUESTION NO: 4

What are some of the characteristics of a typical VLAN arrangement, found throughout the TestKing switched LAN? (Select all that apply)

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A.VLANs logically divide a switch into multiple, independent switches at Layer 2.

B.Trunk links can carry traffic for multiple VLANs.

C.VLAN implementation significantly increases traffic due to added trunking information.

D.A VLAN can span multiple switches.

E.VLANs typically increase the number of switches needed

F.VLANs typically decrease the number of switches needed

Answer: A, B, D Explanation:

VLANs give you the power of making virtual LAN networks to subdivide collision domains into smaller units of functionality, without being limited by physical location.

A is correct because that is the exact function of a VLAN. B is correct because trunk links are used to carry traffic for multiple VLANs. D is correct because a VLAN can and often does span across multiple switches. VTP makes this possible.

Incorrect Answers:

C. Although trunking information does indeed add some level of overhead, the overall traffic overhead is greatly reduced though the use of VLANs.

E, F. The number of total switches needed in a network is the result of the number of devices on the entire LAN that need to be connected. Whether VLANs are used or not will have little, if any, impact on the total number of switches needed in a LAN.

QUESTION NO: 5

How could the TestKing corporation benefit from using VLANs on their network? (Select three answer choices.)

A.VLANs allow access to network services based on department, not physical location.

B.VLANs utilize packet filtering to enhance network security.

C.VLANs provide a low-latency, high bandwidth internetworking alternative.

D.VLANs provide a method of communication between IP addresses in large networks.

E.VLANs establish segmented broadcast domains in switched networks.

F.VLANs can greatly simplify adding, moving, or changing hosts on the network.

Answer: A, E, F

Explanation:

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