3Com 8807 Configuration Manual page 757

By default, no broadcast service is configured and the version number number
defaults to 3.
This command can only be configured on the interface where the NTP broadcast
packets will be transmitted.
Configuring NTP Broadcast Client Mode
Designate an interface on the local Switch to receive NTP broadcast messages and
operate in broadcast client mode. The local Switch listens to the broadcast from
the server. When it receives the first broadcast 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 broadcast client mode and continues listening
to the broadcast and synchronizes the local clock according to the broadcast
message that arrived .
Perform the following configuration in VLAN interface view.
Table 702 Configure NTP broadcast client mode
Operation
Configure NTP broadcast client mode
Disable NTP broadcast client mode
This command can only be configured on the interface where the NTP broadcast
packets will be received.
Configuring NTP Multicast Server Mode
Designate an interface on the local 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 configuration in VLAN interface view.
Table 703 Configure 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 1 to 4294967295; ttl-number of the
multicast packets ranges from 1 to 255; And the multicast IP address defaults to
224.0.1.1. Actually, for the Switch 8800 Family series, you can set 224.0.1.1 as the
multicast IP address only.
This command can only be configured on the interface where the NTP multicast
packet will be transmitted.
Command
ntp-service broadcast-client
undo ntp-service broadcast-client
Command
ntp-service multicast-server [ ip-address ] [
authentication-keyid keyid | ttl ttl-number | version
number ]*
undo ntp-service multicast-server [ ip-address ]
NTP Configuration 757