How do i configure my router to act as a NTP server so that all my xp workstation are able to get the time from this ntp server. And also this ntp server will get the time from the external source.
I have a cisco 1720 router with ADSL connection to the internet
While the ntp master command is the correct way to make a device into an authoritative NTP server, the question indicated that the router would be learning NTP from some external source. In this case it is not necessary (and I would say not wise considering that it is a 1720) to use ntp master on it. If the router is configured with ntp server then it will learn time and will automatically function as an authoritative source of NTP to the clients within the network.
That is not the case. I have configured many routers with ntp server to learn NTP and they then serve time to other clients without needing the ntp master command.
To serve NTP to clients a router needs either to have learned time from an authoritative source OR to be configured with ntp master.
The "ntp master" will instruct the router to include its local clock as a time source, not recomended without a reliable hardware clock.
You can check that the local clock is included in the list of time sources as a stratum 1 time source with the cli command "show ntp associations".
Rui
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