Which three NTP operating modes must the trusted-Key command be configured on for authentication to operate properly? (Choose three.)
Correct Answer: B,C,E
Explanation/Reference:
Explanation:
Client/Server Mode
Configuring an association in client mode, usually indicated by a server declaration in the configuration file, indicates that one wishes to obtain time from the remote server, but that one is not willing to provide time to the remote server.
Symmetric Active/Passive Mode (Peer)
A peer is configured in symmetric active mode by using the peer command and specifying the DNS name or address of the other peer. The other peer is also configured in symmetric active mode in this way.
Note: If the other peer is not specifically configured in this way, a symmetric passive association is activated upon arrival of a symmetric active message. Since an intruder can impersonate a symmetric active peer and inject false time values, symmetric mode should always be authenticated.
Broadcast and/or Multicast Mode
Broadcast mode is intended for configurations involving one or a few servers and a potentially large client population. A broadcast server is configured using the broadcast command and a local subnet address. A broadcast client is configured using the broadcastclient command, allowing the broadcast client to respond to broadcast messages received on any interface. Since an intruder can impersonate a broadcast server and inject false time values, this mode should always be authenticated