Which component of VPN technology ensures that data can be read only by its intended recipient?（）

单项选择题An administrator attempts a traceroute but receives a Destination Unreadable message. Which protocol is responsible for that message?（）

A. RARP
B. RUDP
C. ICMP
D. SNMP

单项选择题When a host transmits data across a network to another host, which process does the data go through?（）

A. standardization
B. conversion
C. encapsulation
D. synchronization

单项选择题A network admin wants to know every hop the packets take when he accesses cisco.com. Which command is the most appropriate to use?（）

A. path cisco.com
B. debug cisco.com
C. trace cisco.com
D. traceroute cisco.com

单项选择题Which line from the output of the show ip interface command indicates a layer 1 problem?（）

A. Serial0/1 is up, line protocol is down
B. Serial0/1 is down, line protocol is down
C. Serial0/1 is up, line protocol is up
D. Serial0/1 is administratively down, line protocol is down

单项选择题Which statement about IPv6 is true?（）

A. Addresses are not hierarchical and are assigned at random.
B. Only one IPv6 address can exist on a given interface.
C. There are 2.7 billion addresses available.
D. Broadcasts have been eliminated and replaced with multicasts.