A. Tunnel IPv6 over IPv4 to connect far-end IPv6 networks
B. Explain why configuring IPv4 and IPv6 at the same time over the same LAN interface is not possible
C. Explain why configuring IPv4 and IPv6 at the same time over the same LAN interface is possible
D. What is the meaning of EUI-64 and how does it work？
E. Tunnel IPv4 over IPv6 to connect far-end IPv4 networks.

A.NTP updates are sent in the timezone they are collected in，and the syslog server will adjust based  on the input time.
B.NTP authentication verifies the source，not the recipient.
C.NTP authentication requires that the recipient has multiple strata clocks to ensure accuracy.
D.Secure NTP can be configured to use SHA-1 hashing，since NTP is very insecure.
E.A stratum 0 clock should be configured at the core of every network，so it can connect to an accuratetime source.