[Free] 2017(July) EnsurePass Examcollection Cisco 200-105 Dumps with VCE and PDF 51-60

2017 July Cisco Official New Released 200-105
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Interconnecting Cisco Networking Devices Part 2 (ICND2 v3.0)

Question No: 51 – (Topic 1)

Which statement about QoS default behavior is true?

  1. Ports are untrusted by default.

  2. VoIP traffic is passed without being tagged.

  3. Video traffic is passed with a well-known DSCP value of 46.

  4. Packets are classified internally with an environment.

  5. Packets that arrive with a tag are untagged at the edge of an administrative domain.

Answer: E

Explanation: Frames received from users in the administratively-defined VLANs are classified or tagged for transmission to other devices. Based on rules that you define, a unique identifier (the tag) is inserted in each frame header before it is forwarded. The tag is examined and understood by each device before any broadcasts or transmissions to other switches, routers, or end stations. When the frame reaches the last switch or router, the tag is removed before the frame is sent to the target end station. VLANs that are assigned on trunk or access ports without identification or a tag are called native or untagged frames.

For IEEE 802.1Q frames with tag information, the priority value from the header frame is used. For native frames, the default priority of the input port is used.

Each port on the switch has a single receive queue buffer (the ingress port) for incoming traffic. When an untagged frame arrives, it is assigned the value of the port as its port default priority. You assign this value by using the CLI or CMS. A tagged frame continues to use its assigned CoS value when it passes through the ingress port.

Topic 2, LAN Switching Technologies

Question No: 52 – (Topic 2)

Refer to the exhibit.


A technician has configured the FastEthernet 0/1 interface on Sw11 as an access link in VLAN 1. Based on the output from the show vlan brief command issued on Sw12, what will be the result of making this change on Sw11?

  1. Only the hosts in VLAN 1 on the two switches will be able to communicate with each other.

  2. The hosts in all VLANs on the two switches will be able to communicate with each other.

  3. Only the hosts in VLAN 10 and VLAN 15 on the two switches will be able to communicate with each other.

  4. Hosts will not be able to communicate between the two switches.

Answer: D Explanation:

VLANs are local to each switch#39;s database, and VLAN information is not passed between switches without implementing VLAN Trunk Protocol (VTP). Trunks carry traffic from all VLANs to and from the switch by default but, can be configured to carry only specified VLAN traffic. Trunk links are required to pass VLAN information between switches. So

Sw11 port should be trunk not access port. Additionally, there are no ports assigned to VLAN 1.

Question No: 53 – (Topic 2)

What is one benefit of PVST ?

  1. PVST supports Layer 3 load balancing without loops.

  2. PVST reduces the CPU cycles for all the switches in the network.

  3. PVST allows the root switch location to be optimized per VLAN.

  4. PVST automatically selects the root bridge location, to provide optimized bandwidth usage.

Answer: C Explanation:

Per VLAN Spanning Tree (PVST)

Introduction http://www.cisco.com/en/US/tech/tk389/tk621/tk846/tsd_technology_support_sub- protocol_home.html

Per VLAN Spanning Tree (PVST) maintains a spanning tree instance for each VLAN configured in the network. This means a switch can be the root bridge of a VLAN while another switch can be the root bridge of other VLANs in a common topology. For example, Switch 1 can be the root bridge for Voice data while Switch 2 can be the root bridge for Video data. If designed correctly, it can optimize the network traffic. http://www.ciscopress.com/articles/article.asp?p=102157amp;seqNum=4

Question No: 54 – (Topic 2)

Refer to the exhibit.


At the end of an RSTP election process, which access layer switch port will assume the discarding role?

  1. Switch3, port fa0/1

  2. Switch3, port fa0/12

  3. Switch4, port fa0/11

  4. Switch4, port fa0/2

  5. Switch3, port Gi0/1

  6. Switch3, port Gi0/2

    Answer: C Explanation:

    In this question, we only care about the Access Layer switches (Switch3 amp; 4). Switch 3 has a lower bridge ID than Switch 4 (because the MAC of Switch3 is smaller than that of Switch4) so both ports of Switch3 will be in forwarding state. The alternative port will surely belong to Switch4.

    Switch4 will need to block one of its ports to avoid a bridging loop between the two switches. But how does Switch4 select its blocked port? Well, the answer is based on the BPDUs it receives from Switch3. A BPDU is superior than another if it has:

    1. A lower Root Bridge ID2. A lower path cost to the Root3. A lower Sending Bridge ID4. A lower Sending Port ID

      These four parameters are examined in order. In this specific case, all the BPDUs sent by Switch3 have the same Root Bridge ID, the same path cost to the Root and the same Sending Bridge ID. The only parameter left to select the best one is the Sending Port ID (Port ID = port priority port index). In this case the port priorities are equal because they use the default value, so Switch4 will compare port index values, which are unique to each port on the switch, and because Fa0/12 is inferior to Fa0/1, Switch4 will select the port connected with Fa0/1 (of Switch3) as its root port and block the other port -gt; Port fa0/11 of

      Switch4 will be blocked (discarding role)

      Question No: 55 – (Topic 2)

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

      1. physical

      2. data link

      3. network

      4. 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. http://www.cisco.com/en/US/tech/tk389/tk621/technologies_white_paper09186a0080094cf a.shtml

Question No: 56 – (Topic 2)

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.)

  1. SwitchA, Fa0/2, designated

  2. SwitchA, Fa0/1, root

  3. SwitchB, Gi0/2, root

  4. SwitchB, Gi0/1, designated

  5. SwitchC, Fa0/2, root

  6. SwitchD, Gi0/2, root

Answer: A,B,F Explanation:

The question says quot;no other configuration changes have been madequot; so we can understand these switches have the same bridge priority. SwitchC has lowest MAC address so, it will become root bridge and 2 of its ports (Fa0/1 amp; Fa0/2) will be designated ports (DP). Because SwitchC is the root bridge the 2 ports nearest SwitchC on SwitchA (Fa0/1) and SwitchD (Gi0/2) will be root ports (RP) -gt; B and F are correct.

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, quot;costquot; 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:

Link speed Cost 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 amp; Gi0/2 of SwitchB to the root bridge. This can be calculated from the quot;cost to the root bridgequot; 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.

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 -gt; Switch B chooses Gi0/1 as its root port.

Now our last task is to identify the port roles of the ports between SwitchA amp; 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.

Question No: 57 – (Topic 2)

Which port state is introduced by Rapid-PVST?

  1. learning

  2. listening

  3. discarding

  4. forwarding

Answer: C Explanation:

Spanning Tree from PVST to Rapid-PVST Migration Configuration Example Reference 1:

http://www.cisco.com/en/US/products/hw/switches/ps708/products_configuration_example 09186a00807b0670.shtml

Reference 2: http://www.cisco.com/en/US/tech/tk389/tk621/technologies_white_paper09186a0080094cf a.shtml

PVST is based on IEEE802.1D Spanning Tree Protocol (STP). But PVST has only 3 port states (discarding, learning and forwarding) while STP has 5 port states (blocking, listening,

learning, forwarding and disabled). So discarding is a new port state in PVST .


Background Information

802.1D Spanning Tree Protocol (STP) has a drawback of slow convergence. Cisco Catalyst switches support three types of STPs, which are PVST , rapid-PVST and MST. PVST is based on IEEE802.1D standard and includes Cisco proprietary extensions such as BackboneFast, UplinkFast, and PortFast. Rapid-PVST is based on IEEE 802.1w standard and has a faster convergence than 802.1D. RSTP (IEEE 802.1w) natively includes most of the Cisco proprietary enhancements to the 802.1D Spanning Tree, such as BackboneFast and UplinkFast. Rapid-PVST has these unique features:

Uses Bridge Protocol Data Unit (BPDU) version 2 which is backward compatible with the 802.1D STP, which uses BPDU version 0.

All the switches generate BPDUs and send out on all the ports every 2 seconds, whereas in 802.1D STP only the root bridge sends the configuration BPDUs.

Port Roles-Root port, designated port, alternate port and backup port. Port States-Discarding, Learning, and Forwarding.

Port Types-Edge Port (PortFast), Point-to-Point and Shared port.

Rapid-PVST uses RSTP to provide faster convergence. When any RSTP port receives legacy 802.1D BPDU, it falls back to legacy STP and the inherent fast convergence benefits of 802.1w are lost when it interacts with legacy bridges.

Question No: 58 – (Topic 2)

Which two states are the port states when RSTP has converged? (Choose two.)

  1. discarding

  2. listening

  3. learning

  4. forwarding

  5. disabled

Answer: A,D Explanation:

Understanding Rapid Spanning Tree Protocol (802.1w)

http://www.cisco.com/en/US/tech/tk389/tk621/technologies_white_paper09186a0080094cf a.shtml

Port States

There are only three port states left in RSTP that correspond to the three possible operational states. The 802.1D disabled, blocking, and listening states are merged into a unique 802.1w discarding state.

RSTP only has 3 port states which are discarding, learning and forwarding. When RSTP has converged there are only 2 port states left: discarding and forwarding.


Question No: 59 – (Topic 2)

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

  1. RSTP cannot operate with PVST .

  2. RSTP defines new port roles.

  3. RSTP defines no new port states.

  4. RSTP is a proprietary implementation of IEEE 802.1D STP.

  5. RSTP is compatible with the original IEEE 802.1D STP.

Answer: B,E Explanation:

http://www.cisco.com/en/US/tech/tk389/tk621/technologies_white_paper09186a0080094cf a.shtml

Port Roles

The role is now a variable assigned to a given port. The root port and designated port roles remain, while the blocking port role is split into the backup and alternate port roles. The Spanning Tree Algorithm (STA) determines the role of a port based on Bridge Protocol Data Units (BPDUs). In order to simplify matters, the thing to remember about a BPDU is there is always a method to compare any two of them and decide whether one is more useful than the other. This is based on the value stored in the BPDU and occasionally on the port on which they are received. This considered, the information in this section explains practical approaches to port roles.

Compatibility with 802.1D

RSTP is able to interoperate with legacy STP protocols. However, it is important to note that the inherent fast convergence benefits of 802.1w are lost when it interacts with legacy bridges.

Question No: 60 – (Topic 2)

Refer to the exhibit.


What commands must be configured on the 2950 switch and the router to allow communication between host 1 and host 2? (Choose two.)

  1. Router(config)# interface fastethernet 0/0 Router(config-if)# ip address Router(config-if)# no shut down

  2. Router(config)# interface fastethernet 0/0 Router(config-if)# no shut down Router(config)# interface fastethernet 0/0.1 Router(config-subif)# encapsulation dot1q 10

    Router(config-subif)# ip address Router(config)# interface fastethernet 0/0.2

    Router(config-subif)# encapsulation dot1q 20

    Router(config-subif)# ip address

  3. Router(config)# router eigrp 100 Router(config-router)# network Router(config-router)# network

  4. Switch1(config)# vlan database Switch1(config-vlan)# vtp domain XYZ Switch1(config-vlan)# vtp server

  5. Switch1(config)# interface fastethernet 0/1 Switch1(config-if)# switchport mode trunk

  6. Switch1(config)# interface vlan 1 Switch1(config-if)# ip default-gateway

Answer: B,E Explanation:

The two answers B and E list all the commands needed to configure interVLAN routing. Please notice that Cisco switch 2950, 2960 only support dot1Q trunking so we don’t need to specify which trunking encapsulation to use in this case. For Cisco switches 3550 or above we have to use these commands instead:

Switch3550(config-if)#switchport trunk encapsulation dot1q Switch3550(config-if)#switchport mode trunk

References: http://www.cisco.com/en/US/tech/tk389/tk815/technologies_configuration_example09186a 00800949fd.shtml

https://learningnetwork.cisco.com/servlet/JiveServlet/download/5669- 2461/Router on a Stick.pdf.

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