NTP

[anand.network]

Can someone please explain about the "NTP"" and its "purpose" and "how it will work" and what are the configuration I have to do in my data center devices..??  

[Philip D'Ath]

It sounds like you want an essay.  Culd you let us know the kind of kit you want to synchronise NTP on?

Short answers:

Purpose: To synchronise the time on devices across a network

How it works: You have various NTP servers of varying levels of trust (the stratum level) and clients talk to 1 or more of these to determine the time.  Note you need 4 NTP servers or more to do really accurate synchronisation (ballantines general problem).

Here is a brief article on SANs that makes interesting reading.

https://www.sans.org/reading-room/whitepapers/protocols/its-about-time-1531

On most Cisco kit you can time synchronisation as a client with:

ntp server a.b.c.d

[anand.network]

Hi Philip,

Thank you for the response, 

Please correct me if am wrong.

I understood, instead of we manually change the time on each routers & switches in our DC, we are using the NTP server, which will do automatic time.

[Philip D'Ath]

Correct.

[anand.network]

Sorry for the trouble, am just a beginner in network, hence basic & clear explanation would be great

[anand.network]

If I have 2 DCs, Do I really need to have the separate NTP server on each DC or placing the NTP in main DC is enough.

[Philip D'Ath]

A DC runs an NTP server, so you can point your Cisco kit at it to get the current date/time.

[anand.network]

So, If I deploy new NTP server, that server has to sync with public NTP servers, hence i have to allow my internal NTP server to access internet, is it right..??

[Philip D'Ath]

It depends on what you want from your time synchronisation.

If you just want all your internal devices to have the same time, so you can compare logs and the like then you don't need to access a public NTP server or Internet access.  You just need to nominate 1 (or more) internal devices to be NTP servers and point everything else at them.

If you want your devices to be synced to the actual time then you get get yourself an actual NTP server with an external reference, such as GPS, and you still don't have to sync against anything on the Internet.

However you you just want to have accurate time at minimum cost, you you do need to sync against a free public NTP server.