The enable secret command is used to secure access to which CLI mode?（）

单项选择题Which statement about vlan operation on cisco catalyst switches is true?（）

 A. when a packet is received from an 802.1Q trunk,the vlan id can be determined from the source MAC address table.
B. unkown unicast frames are retransmitted only to the ports that belong to the same vlan
C. ports between switches should be configured in access mode so that vlans can span across the ports
D. broadcast and multicast frames are retransmitted to ports that are configured on different vlan.

单项选择题A router receives information about network 192.168.10.0 24 from multiple sources.What will the router consider the most reliable information about the path to that network?（）

A. an OSPF update for network 192.168.0.0/16
B. a static router to network 192.168.10.0/24
C. a static router to network 192.168.10.0/24 with a local serial interface configured as the next hop
D. a RIP update for network 192.168.10.0/24
E. a directly connected interface with an address of 192.168.10.254/24
F. a default route with a next hop address of 192.168.10.1

单项选择题A receiving host computes the checksum on a frame and determines that the frame is damaged.The frame is then discarded.At which OSI layer did this happen?（）

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

单项选择题Given an IP address 172.16.28.252 with a subnet mask of 255.255.240.0, what is the correct network addres?（）

A. 172.16.16.0
B. 172.16.24.0
C. 172.16.0.0
D. 172.16.28.0

单项选择题Which command can be used to verify the DLCI destination address in a Frame Relay static configuration?（）

A. show frame-relay end-to-end
B. show frame-relay map
C. show frame-relay lmi
D. show frame-relay pvc