Which two statements about IP Source Guard are true? (Choose two.)
A . It is enabled automatically when DHCP snooping is enabled
B . When it is first enabled, it blocks all IP packets except DHCP packets.
C . It works together with DHCP snooping to verify source IP packets
D . When it is configured on a Layer 2 port channel, it is applied only to the port channel interface.
E . It must be enabled globally for all ports.
F . When it is first enabled, it allows all IP packets except DHCP packets
Answer: BC