3Com Switch 8800 Family Configuration Guide

NTP Configuration 755
■ The delay for a round trip of an NTP packet traveling between Switch A and B:
Delay= (T
4
-T
1
) - (T
3
-T
2
).
■ Offset of Switch A clock relative to Switch B clock: offset= ( (T
2
-T
1
) + (T
4
-T
3
) ) /2.
In this way, Switch A uses the above-mentioned information to set the local clock
and synchronize it with the clock on Switch B.
The operating principle of NTP is briefly introduced above. For details, refer to
RFC1305.
NTP Configuration NTP is used for time synchronization throughout a network. The following sections
describe the NTP configuration tasks.
■ “Configuring NTP Operating Mode”
■ “Configuring NTP ID Authentication”
■ “Setting NTP Authentication Key”
■ “Setting Specified Key as Reliable”
■ “Designating an Interface to Transmit NTP Messages”
■ “Setting NTP Master Clock”
■ “Setting Authority to Access a Local Switch”
■ “Setting Maximum Local Sessions”
Configuring NTP
Operating Mode
You can set the NTP operating mode of a Switch according to its location in the
network and the network structure. The following settings are for your reference:
■ If you set a remote server as the time server of the local equipment, the local
Switch works as an NTP Client.
■ If you set a remote server as a peer of the local Switch, the local equipment
operates in Symmetric Active mode.
■ If you configure an interface on the local Switch to transmit NTP broadcast
packets, the local Switch will operate in Broadcast mode.
■ If you configure an interface on the local Switch to receive NTP broadcast
packets, the local Switch will operate in Broadcast Client mode.
■ If you configure an interface on the local Switch to transmit NTP multicast
packets, the local Switch will operate in Multicast mode.
■ If you configure an interface on the local Switch to receive NTP multicast
packets, the local Switch will operate in Multicast Client mode.
To configure NTP:
■ Configure NTP server mode
■ Configure NTP peer mode
■ Configure NTP broadcast server mode
■ Configure NTP broadcast client mode
■ Configure NTP multicast server mode
■ Configure NTP multicast client mode