A.It may allocate IP addresses from an unknown subnet to the users.
B.All multicast traffic can be sniffed by using the DHCP multicast capabilities.
C.The CPU utilization of the first hop router can be overloaded by exploiting DHCP relay open ports.
D.A potential man-in-the-middle attack can be used against the clients.

A. 1） lowest root bridge id，2）lowest sender bridge id，3）lowest port id，4）lowest root path cost
B. 1） lowest root path cost，2）lowest root bridge id，3）lowest sender bridge id，4）lowest sender port id
C. 1） lowest root bridge id，2）lowest sender bridge id，3）lowest root path cost 4）owest sender port id
D. 1） lowest root bridge id，2）lowest root path cost，3）lowest sender bridge id，4）lowest sender port id

A. VTP updates are ignored and forwarded out all ports.
B. VTP updates are ignored and forwarded out trunks only.
C. VTP updates are made to the VLAN database and are forwarded out trunks only.
D. VTP updates are ignored and are not forwarded.

A.Increase the shaping rate for the priority queue.
B.Remove the policer applied on the priority queue.
C.Remove the shaper applied on the priority queue.
D.Increase the policing rate for the priority queue.

A.enforce the placement of the root bridge in the network
B.ensure that a port is transitioned to a forwarding state quickly if a BPDU is received
C.enforce the borders of an STP domain
D.ensure that any BPDUs received are forwarded into the STP domain