What are two reasons a network administrator would use CDP? （）

• A、to verify the type of cable interconnecting two devices
• B、to determine the status of network services on a remote device
• C、to obtain VLAN information from directly connected switches
• D、to verify Layer 2 connectivity between two devices when Layer 3 fails
• E、to obtain the IP address of a connected device in order to telnet to the device
• F、to determine the status of the routing protocols between directly connected routers