A.Configure SNMP with only read-only community strings.
B.Encrypt TFTP and syslog traffic in an IPSec tunnel.
C.Implement RFC 3704 filtering at the perimeter router when allowing syslog access from devices on the outside of a firewall.
D.Synchronize the NTP master clock with an Internet atomic clock.
E.Use SNMP version 2.
F.Use TFTP version 3 or above because these versions support a cryptographic authentication mechanism between peers.

A.A received IP packet is forwarded based on the IP destination address and the packet is sent as an IP packet.
B.An IP destination exists in the IP forwarding table. A received labeled packet is dropped because the label is not found in the LFIB table.
C.There is an MPLS label-switched path toward the destination. A received IP packet is dropped because the destination is not found in the IP forwarding table.
D.A received IP packet is forwarded based on the IP destination address and the packet is sent as a labeled packet.
E.A received labeled IP packet is forwarded based upon both the label and the IP address.
F.A received labeled packet is forwarded based on the label. After the label is swapped，the newly labeled packet is sent.