3Com Switch 7700 Configuration Manual page 369

This command can only be configured on the interface where the NTP broadcast
packets are received.
Configuring NTP Multicast Server Mode
switch to transmit NTP multicast packets. In this case, the local equipment
operates in multicast mode and serves as a multicast server to multicast messages
to its clients regularly.
Perform the following configurations in VLAN interface view.
Table 69 Configuring NTP Multicast Server Mode
Operation
Configure NTP multicast server mode
Cancel NTP multicast server mode
NTP version number number ranges from 1 to 3 and defaults to 3; the
authentication key ID keyid ranges from 0 to 4294967295; ttl-number of the
multicast packets ranges from 1 to 255; And the multicast IP address defaults to
224.0.1.1.
This command can only be configured on the interface where the NTP multicast
packet is transmitted.
Configuring NTP Multicast Client Mode
switch to receive NTP multicast messages and operate in multicast client mode.
The local switch listens to the multicast from the server. When it receives the first
multicast packets, it starts a brief client/server mode to switch messages with a
remote server for estimating the network delay. Thereafter, the local switch enters
multicast client mode and continues listening to the multicast and synchronizes
the local clock by the arrived multicast message.
Perform the following configurations in VLAN interface view.
Table 70 Configuring NTP Multicast Client Mode
Operation
Configure NTP multicast client mode
Cancel NTP multicast client mode
Multicast IP address ip-address defaults to 224.0.1.1. This command can only be
configured on the interface where the NTP multicast packets is received.
Configuring NTP ID Authentication
Enable NTP authentication, set the MD5 authentication key, and specify the
reliable key. A client will synchronize itself by a server only if the server can provide
a reliable key.
Designate an interface on the local
Command
ntp-service multicast-server [ ip-address ] [
authentication-keyid keyid ] [ ttl ttl-number
] [ version number ]
undo ntp-service multicast-server
Designate an interface on the local
Command
ntp-service multicast-client [ ip-address ]
undo ntp-service multicast-client
NTP 361