Refer to the exhibit. Switch 15 is configured as the root switch for VLAN 10 but not for VLAN 20. If the STP configuration is correct， 
what will be true about Switch 15？（）

多项选择题WhichtwostatementsaretrueaboutBPDUport-guardandBPDUfiltering？（）

A.BPDU port-guard can be enabled globally， whereas BPDU filtering must be enabled on a per-interface basis.
B.When globally enabled， BPDU port-guard and BPDU filtering apply only to PortFast enabled ports.
C.When globally enabled， BPDU port-guard and BPDU filtering apply only to trunking-enabled ports.
D.When a BPDU is received on a BPDU port-guard enabled port， the interface goes into the err-disabled state.
E.When a BPDU is received on a BPDU filtering enabled port， the interface goes into the err-disabled state.
F.When a BPDU is received on a BPDU filtering enabled port， the interface goes into the STP blocking state.

单项选择题Refer to the exhibit and the partial configuration of switch SW_A and SW_B. STP is configured on all switches in the network. SW_B receives this error message on the console port： 00：06：34： %CDP-4-DUPLEX_MISMATCH： duplex mismatch discovered on FastEthernet0 5 （not half  duplex）， with SW_A FastEthernet0 4 （half duplex） ， with TBA05071417（Cat6K-B） 0 4 （half duplex）.  What would be the possible outcome of the problem？（）

A.The root port on switch SW_A will automatically transition to full-duplex mode.
B.The root port on switch SW_B will fallback to full-duplex mode.
C.The interfaces between switches SW_A and SW_B will transition to a blocking state.
D.Interface Fa 0/6 on switch SW_B will transition to a forwarding state and create a bridging loop.

多项选择题WhichtwostatementsaboutthevariousimplementationsofSTParetrue？（）

A.mon Spanning Tree maintains a separate spanning-tree instance for each VLAN configured in the network.
B.The Spanning Tree Protocol （STP） is an evolution of the IEEE 802.1w standard.
C.Per-VLAN Spanning Tree （PVST） supports 802.1Q trunking.
D.Per-VLAN Spanning Tree Plus（PVST+） is an enhancement to 802.1Q specification and is supported only on Cisco devices.
E.Rapid Spanning Tree Protocol （RSTP） includes features equivalent to Cisco PortFast， UplinkFast， and BackboneFast for faster network reconvergence.
F.Multiple Spanning Tree （MST） assumes one spanning-tree instance for the entire Layer 2 network， regardless of the multiple number of VLANs

单项选择题Refer to the exhibit. For what purpose is the command show ip cef used？（）

A.to display rewritten IP unicast packets
B.to display ARP resolution packets
C.to display ARP throttling
D.to display TCAM matches
E.to display CEF-based MLS lookups
F.to display entries in the Forwarding Information Base （FIB）

单项选择题Refer to the exhibit. Which statement is true about the output？（）

A.The port on switch CAT1 is forwarding and sending BPDUs correctly.
B.The port on switch CAT1 is blocking and sending BPDUs correctly.
C.The port on switch CAT2 is forwarding and receiving BPDUs correctly.
D.The port on switch CAT2 is blocking and sending BPDUs correctly.
E.The port on switch CAT3 is forwarding and receiving BPDUs correctly.
F.The port on switch CAT3 is forwarding， sending， and receiving BPDUs correctly.