At which layer of the OSI model is RSTP used to prevent loops?（）

多项选择题Which three statements about RSTP are true?（）

A.RSTP significantly reduces topology reconverging time after a link failure.
B.RSTP expends the STP port roles by adding the alternate and backup roles.
C.RSTP port satates are blocking,discarding,learing,or forwarding.
D.RSTP also uses the STP proprsal-agreement sequence.
E.RSTP use the same timer-baseed process as STP on point-to-point links.
F.RSTP provides a faster transition to the forwarding state on point-to-point links than STP does.

单项选择题Refer to the exhibit A frame on vlan 1 on switch s1 is sent to switch s2 when the frame is received on vlan 2,what causes this behavior?（）

A.trunk mode mismatches
B.vlans that do not correspond to a unique IP subnet
C.native vlan mismatches
D.allowing only vlan 2 on the destination.

多项选择题Refer to the topology shown in the exhibit. Which ports will be STP designated ports if all the links are operating at the same bandwidth? （）

A.Switch A - Fa0/0
B.Switch A - Fa0/1
C.Switch B - Fa0/0
D.Switch B - Fa0/1
E.Switch C - Fa0/0
F.Switch C - Fa0/1

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assuming the default switch configuration which vlan range can be added modified and removed on a cisco switch?（）

A.2 through 1001
B.1 through 1001
C.1 through 1002
D.2 through 1005