Cisco WS-C2960-24TC-L Software Guide - Page 576
Default NTP Configuration, Configuring NTP on the Switch, Enabling NTP in Broadcast-Client Mode
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Default NTP Configuration Chapter 39 Configuring NTP The communications between machines running NTP, known as associations, are usually statically configured; each machine is given the IP addresses of all machines with which it should form associations. An associated pair of machines can keep accurate timekeeping by exchanging NTP messages between each other. However, in a LAN environment, you can configure NTP to use IP broadcast messages. With this alternative, you can configure the machine to send or receive broadcast messages, but the accuracy of timekeeping is marginally reduced because the information flow is one-way only. Cisco's implementation of NTP does not support stratum 1 service; it is not possible to connect to a radio or atomic clock. We recommend that you obtain the time service for your network from the public NTP servers available on the IP Internet. If the network is isolated from the Internet, Cisco's NTP implementation allows a machine to be configured so that it acts as though it is synchronized using NTP, when it actually has determined the time using other methods. Other machines synchronize to that machine using NTP. Default NTP Configuration Table 39-1 shows the default NTP configuration. Table 39-1 Default NTP Configuration Feature Broadcast client mode Client mode Broadcast delay Time zone Offset from UTC Summertime adjustment NTP server Authentication mode Default Value Disabled Disabled 3000 microseconds Not specified 0 hours Disabled None specified Disabled Configuring NTP on the Switch The following sections describe how to configure NTP. Enabling NTP in Broadcast-Client Mode Enable the switch in NTP broadcast-client mode if an NTP broadcast server, such as a router, regularly broadcasts time-of-day information on the network. To compensate for any server-to-client packet latency, you can specify an NTP broadcast delay (a time adjustment factor for the receiving of broadcast packets by the switch). 39-2 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 78-15486-01
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