A.Before MPLS is enabled， the ip cef command is only requited on routers 1 and 4
B.After MPLS is enabled， the ip cef command is only required on routers 1 and 4
C.Before MPLS is enabled， the ip cef command is only required on the Ethernet 0 interfaces ofrouters 1 and 4
D.After MPLS is enabled， the ip cef command is only required on the Ethernet 0 interfaces ofrouters 1 and 4
E.Before MPLS is enabled， the ip cef command must be applied to all provider routers

A.To prevent customers from running TDP with the ISP routers
B.To prevent customers from running LDP with the ISP routers
C.To prevent other ISPs from running LDP with the ISP routers
D.To prevent man-in-the-middle attacks
E.To use CBAC to shut down Distributed Denial of Service attacks
F.To use IPS to protect against session-replay attacks
G.None of the above