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

单项选择题What is the function of the command switchport trunk native vlan 999 on a switch?（）

A.It designates VLAN 999 for untagged traffic.
B.It blocks VLAN 999 traffic from passing on the trunk.
C.It creates a VLAN 999 interface.
D.It designates VLAN 999 as the default for all unkown tagged traffic.

单项选择题Refer to the exhibit.Switch-1 needs to send data to a host with a MAC address of 00b0.d056.efa4.What will Switch-1 do with this data?（）

A.switch-1 will drop the data because it dose not have an entry for that MAC address
B.switch-1 will flood the data out all of its port from which the data originated
C.switch-1 will forward the data to its default gateway
D.tch-1 will send an ARP request out all its ports except the port from which the data originated

单项选择题What value is primarily used to determine which port becomes the root port on each nonroot switch in a spanning-tree topology?（）

A.lowest port MAC address
B.port priority number and MAC address.
C.VTP revision number
D.highest port priority number.
E.path cost

单项选择题Refer to the exhibit. Based on the information given. Which switch will be elected root bridge and why?（）

A.Switch A ,because it has the lowest MAC address
B.Switch C,because it has the lowest priority
C.Switch B,because it has the highest MAC address
D.Switch C,because it is the most centrally located switch
E.Switch A,because it is the most centrally located switch
F.Switch D,because it has the highest priority

多项选择题For what two purposes does the Ethernet protocol use physical addresses? （）

A.to uniquely identify devices at Layer 2
B.to allow communication with devices on a different network
C.to differentiate a Layer 2 frame from a Layer 3 packet
D.to establish a priority system to determine which device gets to transmit first
E.to allow communication between different devices on the same network
F.to allow detection of a remote device when its physical address is unknown