You are unable to telnet to a router at address 203.125.12.1 from a workstation with the IP address 203.125.12.23. You suspect that there is a problem with your protocol stack. Which of the following actions is most likely to confirm your diagnosis?（）

单项选择题Why would an administrator change the value of the spanning-tree priority of a switch?（）

A. in order to optimize the path that frames take from source to destination
B. to increase the priority so a designated port will become a root port
C. to increase the BID, so the switch is more likely to become root bridge
D. in order to allow VLANs to be sent from one switch to another across a single link
E. to force a given switch to become an STP server

多项选择题Which of the following components must be elected before the Spanning Tree Protocol can converge in a switched LAN?（）

A. designated ports.
B. duplex operating mode.
C. fast mode ports.
D. root bridge.
E. root ports.
F. BDPU priority.

单项选择题What is the subnetwork number of a host with an IP address of 172.16.210.0 22?（）

A. 172.16.42.0
B. 172.16.107.0
C. 172.16.208.0
D. 172.16.252.0
E. 172.16.254.0

多项选择题Which statements describe the routing protocol OSPF?（）

A. It supports VLSM.
B. It is used to route between autonomous systems.
C. It confines network instability to one area of the network.
D. It increases routing overhead on the network.
E. It allows extensive control of routing updates.
F. It is simpler to configure than RIP v2.

单项选择题On point-to-point networks, OSPF hello packets are addressed to which address?（）

A.127.0.0.1
B.172.16.0.1
C.192.168.0.5
D.223.0.0.1
E.224.0.0.5
F.254.255.255.255