3Com S7906E Configuration Manual page 2549

For the client/server mode, if the NTP authentication feature has not been enabled for the client,
the client can synchronize with the server regardless of whether the NTP authentication feature
has been enabled for the server or not. If the NTP authentication is enabled on a client, the client
can be synchronized only to a server that can provide a trusted authentication key.
For all synchronization modes, the server side and the client side must be consistently configured.
Configuration Procedure
Configuring NTP authentication for a client
Follow these steps to configure NTP authentication for a client:
To do...
Enter system view
Enable NTP authentication
Configure an NTP
authentication key
Configure the key as a trusted
key
Associate the specified key
with an NTP server
After you enable the NTP authentication feature for the client, make sure that you configure for the client
an authentication key that is the same as on the server and specify that the authentication key is trusted;
otherwise, the client cannot be synchronized to the server.
Configuring NTP authentication for a server
Follow these steps to configure NTP authentication for a server:
To do...
Enter system view
Enable NTP authentication
Use the command...
system-view
ntp-service authentication
enable
ntp-service
authentication-keyid keyid
authentication-mode md5
value
ntp-service reliable
authentication-keyid keyid
Client/server mode:
ntp-service unicast-server
{ ip-address | server-name }
authentication-keyid keyid
Symmetric peers mode:
ntp-service unicast-peer
{ ip-address | peer-name }
authentication-keyid keyid
Use the command...
system-view
ntp-service authentication
enable
1-15
Remarks
—
Required
Disabled by default
Required
No NTP authentication key by
default
Required
No authentication key is
configured to be trusted by
default.
Required
You can associate a
non-existing key with an NTP
server. To enable NTP
authentication, you must
configure the key and specify it
as a trusted key after
associating the key with the
NTP server.
Remarks
—
Required
Disabled by default