A.user EXEC mode
B.global configuration mode
C.privileged EXEC mode
D.auxiliary setup mode

A.application
B.internet
C.network
D.transport

A.blocking
B.learning
C.disabled
D.forwarding
E.listening

A.Router（config）#router ospf 1
B.Router（config）#router ospf 0
C.Router（config）#router ospf  area 0
D.Router（config-router）#network 192.168.16.0 0.0.0.255 area 0
E.Router（config-router）#network 192.168.16.0 0.0.0.255 0
F.Router（config-router）#network 192.168.16.0 255.255.255.0 area 0

A.510
B.1022
C.1024
D.2048

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

A.192.0.2.0
B.192.0.2.255
C.192.0.3.255
D.192.0.4.0

A.192.168.8.25
B.192.168.8.41
C.192.168.8.49
D.192.168.8.113

A.DLCI 17 describes the ISDN circuit between R2 and R3.
B.DLCI17 describes a PVC on R2.It cannot be used on R3 or R1.
C.DLCI17 is the Layer 2 address used by R2 to describe a PVC to R3.
D.DLCI17 describes the dial-up circuit from R2 and R3 to the service provider.

A.show session
B.show cdp neighbors
C.show users
D.show queue