avoid Layer 2 loops. Which two of the following are most probably the reasons for that preference?（）

相似题目

• Which two protocols are used by bridges and/or switches to prevent loops in a layer 2 network?（）

  A . 802.1d B . VTP C . 802.1q D . STP E . SAP

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• Which three Layer 2 encapsulation types would be used on a WAN rather than a LAN (Choose three.)（）。

  A . HDLC B . Ethernet C . Token Ring D . PPP E . FDDI F . Frame Relay

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• Which three statements accurately describe layer 2 Ethernet switches？（）

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

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• Which two differentiators make RSTP the preferred protocol for preventing Layer 2 loops in a switchednetwork environment?（） (Choose two.)

  A . Features such as UplinkFast and BackboneFast are compatible with RSTP. B . An RSTP that is based on Cisco products generally performs better than the Cisco proprietary 802.1D enhancements. C . Cisco proprietary enhancements are not transparent. D . Information about port roles is sent to all switches. E . RSTPs that are based on Cisco products require no additional configuration.

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• At Layer 2 of the OSI model, which component connects a host to the network media?（）

  A . Hub B . Switch C . Bridge D . NIC E . Transceiver

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• Which description is correct for a private VLAN community port with respect to Layer 2 communications？（）   

  A .  It communicates with all other community ports in the private VLAN domain. B .  It communicates with only isolated ports in the private VLAN domain. C .  It communicates only with other community ports in the same community and associated promiscuous ports. D .  It communicates only with associated promiscuous and isolated ports.

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• Which three Layer 2 encapsulation types would be used on a WAN rather than a LAN?（）

  A . HDLC B . Ethernet C . Token Ring D . PPP E . FDDI F . Frame Relay

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• The Company is concerned about Layer 2 security threats.  Which statement is true about these  threats？ （）

  A .  MAC spoofing attacks allow an attacking device to receive frames intended for a different  network host. B .  Port scanners are the most effective defense against dynamic ARP inspection. C .  MAC spoofing, in conjunction with ARP snooping, is the most effective counter-measure against reconnaissance attacks that use dynamic ARP inspection (DAI) to determine vulnerable  attack points. D .  Dynamic ARP inspection in conjunction with ARP spoofing can be used to counter DHCP  snooping attacks. E .  DHCP snooping sends unauthorized replies to DHCP queries. F .  ARP spoofing can be used to redirect traffic to counter dynamic ARP inspection. G .  None of the other alternatives apply.

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• Loop guard and UniDirectional Link Detection both protect against Layer 2 STP loops. In which two ways does loop guard differ from UDLD in loop detection and prevention？ （）

  A .  Loop guard can be used with root guard simultaneously on the same port on the same VLAN while UDLD cannot B .  UDLD protects against STP failures caused by cabling problems that create one-way links. C .  Loop guard detects and protects against duplicate packets being received and transmitted on different ports D .  UDLD protects against unidirectional cabling problems on copper and fiber media. E .  Loop guard protects against STP failures caused by problems that result in the loss of BPDUs from a designated switch port.

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• When NIC teaming is used ,how are loops avoided in a virtual switch?（）

  A . By using active / passive teaming with spanning tree on the active link B . By using active / passive teaming with only the active link in use C . By using active / active teaming with VM utilizing both uplink port

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• Which three statements about classification marking of traffic at Layer 2 are true？ （）

  A . a Frame Relay header includes a 1-bit discard eligible （DE） bit to provide the class of service （CoS） B . an ATM header includes a 1-bit DE field to provide the CoS C . an MPLS EXP field is inserted in the Layer 3 IP precedence field to identify the CoS D . the CoS field only exists inside Ethernet frames when 802.1Q or Inter-Switch Link （ISL） trunking is used E . in the IEEE 802.1p standard， three bits are used to identify the user priority bits for the CoS F . in the IEEE 802.1q standard， six bits are used to identify the user priority bits for the CoS

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• Which layer 2 protocol encapsulation type supports synchronous and asynchronous circuis and has built-in security mechanisms?（）

  A . Frame Relay B . HDLC C . x.25 D . PPP

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• Which three Layer 2 access designs have all of their uplinks in an active state?（）

  A . Flex Links B . loop-free U C . looped square D . looped triangle E . loop-free inverted U

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• When you design QoS on CE for an MPLS Layer 2 VPN， which three things should be considered？（）

  A . Layer 2 access link QoS design B . enterprise-to-service-provider mapping models C . Layer 3 link access QoS design D . service provider service level agreements E . Layer 2 link access load balancing

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• Which of the following troubleshooting targets is considered to be a Layer 2 issue？（Choose allthat apply.）（）

  A . Spanning Tree Protocol B . Cabling C . Frame forwarding D . Packet forwarding E . EtherChannel F . Routing protocol

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• Which three Layer 2 access designs have all of their uplinks in an active state？（）

  A . Flex Links B . loop-free U C . looped square D . looped triangle E . loop-free inverted U

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• Which IOS features are used to avoid Routing loops when dynamic Routing protocols are used betweenPE and CE in MPLS-VPN networks？（）

  A . Site Of Origin SOO. B . SHAM links with OSPF C . BGP cost community D . BGP feature allow-as in E . RPF Reverse Path forwarding. F . Access-list Control in Distance Vector protocol like RIP and EIGRP.

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• Loop guard and UniDirectional Link Detection both protect against Layer 2 STP loops. In which two ways does loop guard differ from UDLD in loop detection and prevention？（）

  A . Loop guard can be used with root guard simultaneously on the same port on the same VLAN while UDLD cannot. B . UDLD protects against STP failures caused by cabling problems that create one-way links. C . Loop guard detects and protects against duplicate packets being received and transmitted on different ports. D . UDLD protects against unidirectional cabling problems on copper and fiber media. E . Loop guard protects against STP failures caused by problems that result in the loss of BPDUs from a designated switch port.

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• Which command alone will disable trunking on a Layer 2 switch port？（）

  A . no switchport trunk native vlan vlan-id B . switchport nonegotiate C . no switchport mode dynamic desirable D . switchport mode acce

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• Which three Layer 2 encapsulation types would be used on a WAN rather than a LAN? (Choose three.)（）

  A . HDLC B . Ethernet C . Token Ring D . PPP E . FDDI F . Frame Relay

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• When NIC teaming is used, how are Loops avoided in a virtual switch?（）

  A . By using active / passive teaming with spanning tree on the active Iink B . By using active / passive teaming with onIy the active Iink in use C . By using active / activate teaming with VM utilizing both uplink port

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

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

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• Which tech nology manages multicast traffic at Layer 2 by configuring Layer 2 LAN interfaces dynamically to forward multicast traffic only to those interfaces that want to receive it?（）

  A . IGMP B . IGMP snooping C . PIM - DM D . DVMRP E . MOS PF

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• Which three statements accurately describe layer 2 Ethernet switches?（）

  A . Microsegmentation decreases the number of collisions on the network. B . if a switch receives a frame for an unkown destination,it uses ARP to resolve the address. C . Spanning Tree Protocol allows switches to automatically share vlan information. D . In a properly functioning network with redundant switched paths,each switched aegment 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. E . Establishing vlans increases the number of broadcast domains. F . Switches that are configured with vlans make forwarding decisions based on both layer 2 and layer 3 address information.

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