ActualTests.Cisco.640-802.Exam.Q.and.A.08.15.08-DDU (1130589), страница 21
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Port FA1/1 of both the switches CK2 and CK3will become ROOT ports because they have minimum path cost to reach the root bridge.So, choices D and E are also wrong.Next Election will be of Designated Ports on the segment connecting CK2 and CK3 . CK2has lower MAC address so, its port FA1/2 will become designated port and FA1/2 ofCK3 will be placed in a BLOCKING state to avoid switching LOOPS.QUESTION 176:Four Certkiller switches are connected together as shown below:The network shown in the exhibit was designed to provide reliability throughredundancy.
Both of the IDF switches, CK3 , and CK4 , are connected to both of theMDF switches, CK1 and CK2 . Which configuration scenario will provide a loop-freeswitching environment?A. Spanning Tree Protocol should be running on all switches.B. Spanning Tree Protocol should be running on only the MDF switches CK1 and CK2 .C. Spanning Tree Protocol should be running on only the IDF switches CK3 and CK4 .D. Spanning Tree Protocol should be run only on the root bridge.E. Spanning Tree Protocol is not needed in this network.Answer: AExplanation:Spanning-Tree Protocol (STP) prevents loops from being formed when switches orbridges are interconnected via multiple paths.
Spanning-Tree Protocol implements theActualtests.com - The Power of Knowing640-802802.1D IEEE algorithm by exchanging BPDU messages with other switches to detectloops, and then removes the loop by shutting down selected bridge interfaces. Thisalgorithm guarantees that there is one and only one active path between two networkdevices.Reference:http://www.cisco.com/en/US/tech/ CK3 89/ CK6 21/tsd_technology_support_protocol_home.htmlQUESTION 177:Four Certkiller switches are connected together as shown in the diagram below:Study the Exhibit carefully. What is the purpose of the Spanning Tree Protocol thatis operating in the exhibited switch topology?A.
To elect a particular switch as backup designated switch.B. To have one active Layer 2 path through the switches network.C. To select the best path to a remote destination that is on a different network.D. To learn the MAC addresses of host attached to the switches network.E. To distribute VLAN configuration information throughout the switched network.Answer: BExplanation:Switches are connected in a way to provide full-mesh topology. So, a redundant path isprovided in the case of a link or switch failure.
The STP is used to prevent frames fromlooping throughout the network.QUESTION 178:When is a switched network that is running the Spanning Tree Protocol consideredto be fully converged?A. when all switches have the same BID as the root switchB. when all switches have received the MAC address of each neighboring switchC.
when every enabled switch port has been assigned a unique identifierD. when every operating switch port is in either the blocking or forwarding stateActualtests.com - The Power of Knowing640-802E. when all switches are in either client, server, or transparent modeAnswer: DExplanation:States of the Spanning Tree Protocol:Blocking A blocked port won't forward frames; it just listens to BPDUs. All ports are inblocking state by default when the switch is powered up. The purpose of the blockingstate is to prevent the use of looped paths.Listening The port listens to BPDUs to make sure no loops occur on the network beforepassing data frames.
A port in listening state prepares to forward data frames withoutpopulating the MAC address table.Learning The switch port listens to BPDUs and learns all the paths in the switchednetwork. A port in learning state populates the MAC address table but doesn't forwarddata frames.Forwarding The port sends and receives all data frames on the bridged port.Disabled A port in the disabled state does not participate in the frame forwarding or STP.A port in the disabled state is virtually non-operational.In Blocking States, all ports are in blocking state. The purpose of the blocking state is toprevent the use of looped paths. The forward state sends and receives the all data framesin a loop free network.
So these two states are considered to be fully converged.QUESTION 179:Exhibit:.Based on the output from the show spanning-tree command shown, what can bedetermined about the switch configuration? (Choose two.)Actualtests.com - The Power of Knowing640-802A. This switch is the root bridge for VLA.N 1B. The 802.1d protocol is enabled on the switchC. This switch is connected to port 17 on the root bridgeD.
The switches are using Rapid Spanning Tree ProtocolE. Port 17 is the root port and port 23 is the redundant linkAnswer: B, EThe answer shows that the bridge output is the root bridge for VLAN 1. If that were thecase, then there would be no blocked ports for this output. Also, the Root ID and BridgeID would have the same Address.QUESTION 180:Exhibit:Based on the information shown above, what can be determined from the outputshown?A. The Certkiller 1 switch is using VTP.B. This is the only switch in the LAN topology.C. The Certkiller 1 switch is not the root switch.D.
The link to the root bridge is through a 1 Gbps connection.E. Spanning Tree Protocol is disabled on the Certkiller 1 switch.Answer: CExplanation:The root ID of the switch is the default root ID assigned to all Cisco switches, in order toforce this switch to become the Root switch you may issue the spanning-tree vlan 1priority [0-61440 in increments of 4096] command.QUESTION 181:Actualtests.com - The Power of Knowing640-802What is the purpose of the Spanning Tree Protocol (STP)?A.
To prevent routing loopsB. To create a default routeC. To provide multiple gateways for hostsD. To maintain a loop-free Layer 2 network topologyE. To enhance the functions of SNMPAnswer: DExplanation:STP's main task is to stop network loops from occurring on your Layer 2 network(bridges or switches). It vigilantly monitors the network to find all links, making sure thatno loops occur by shutting down any redundant ones.
STP uses the spanning-treealgorithm (STA) to first create a topology database, then search out and destroyredundant links. With STP running, frames will only be forwarded on the premium,STP-picked links.QUESTION 182:The Certkiller network is shown below:How will Spanning Tree affect the operation of the network devices shown in thegraphic?A. Spanning Tree will block client ports that suffer from excessive errors.B.
Spanning Tree will learn client MAC addresses and assign them to switch ports.C. Spanning Tree will allow these switches to load balance across the redundant links toincrease network throughput.D. Spanning Tree will learn which of the redundant links should be blocked.E. Spanning tree will automatically configure the switches with VLAN information.Answer: DExplanation:STP states are as follows:Disabled-Ports that are administratively shut down by the network administrator, or by thesystem due to a fault condition, are in the Disabled state. This state is special and is notpart of the normal STP progression for a port.Actualtests.com - The Power of Knowing640-802Blocking-After a port initializes, it begins in the Blocking state so that no bridging loopscan form.
In the Blocking state, a port cannot receive or transmit data and cannot addMAC addresses to its address table. Instead, a port is allowed to receive only BPDUs sothat the switch can hear from other neighboring switches. In addition, ports that are putinto standby mode to remove a bridging loop enter the Blocking state.Listening-The port will be moved from Blocking to Listening if the switch thinks that the port can beselected as a Root Port or Designated Port. In other words, the port is on its way to begin forwardingtraffic. In the Listening state, the port still cannot send or receive data frames.
However, the port is allowedto receive and send BPDUs so that it can actively participate in the Spanning Tree topology process. Here,the port is finally allowed to become a Root Port or Designated Port because the switch can advertise theport by sending BPDUs to other switches.
Should the port lose its Root Port or Designated Port status, itreturns to the Blocking state.Learning-After a period of time called the Forward Delay in the Listening state, the port is allowed tomove into the Learning state. The port still sends and receives BPDUs as before. In addition, the switchcan now learn new MAC addresses to add to its address table. This gives the port an extra period of silentparticipation and allows the switch to assemble at least some address table information.Forwarding-After another Forward Delay period of time in the Learning state, the port isallowed to move into the Forwarding state.
The port can now send and receive dataframes, collect MAC addresses in its address table, and send and receive BPDUs. Theport is now a fully functioning switch port within the Spanning Tree topology.QUESTION 183:Four Certkiller switches are shown below:Assuming these are the only four switches in the network and the switches areconnected with redundant links, which switch will be elected as the spanning-treeroot bridge?Actualtests.com - The Power of Knowing640-802A. Certkiller 1B. Certkiller 2C. Certkiller 3D.
Certkiller 4Answer: AExplanation:To elect the root bridge in the LAN, first check the priority value. The switch havinglowest priority will win the race. If Priority Value is same then it checks the MACAddress, the switch having lowest MAC Address will be the root bridge.
Here Switch 1has the lowest MAC Address so it becomes the root bridge.QUESTION 184:Four Certkiller switches are shown below:The bridge ID for each switch and the bandwidth for each link is shown. Assumingthat all switches are set to the default configuration, which ports will be blockingwhen Spanning Tree has converged? (Choose three.)A.
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