different source addresses for getting and providing NTP

[Michal Rzepecki]

HI

How to configure one router to get time from NTP server using Lo1

and

provide time using Lo2 ?

[Karsten Iwen]

With

rtr(config)#ntp server 192.53.103.104 source Loopback1

you tell the router to use a specific source-address. And if there is no access-control in place other systems can use any of the router-addresses (including L2 as you want) to get the time from the router.

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[Michal Rzepecki]

So if other router (i.e. rtrB) starts synchronizing to rtr loopback2

rtr configuration

rtr(config)#ntp server 192.53.103.104 source Loopback1

rtr(config)#ntp master

doesn't mean that rtr have to respond using loopback1 source address ?

[Karsten Iwen · Accepted solution]

No, the router responds with the address that is used by the ntp-client (which will be Lo2 for your setup). The parameter "source Lo1" is only used for his own ntp-client-connectivity. And you don't need the command "ntp master" if your router has a valid time-source.

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[Michal Rzepecki]

thanks for clarification

[Leo Laohoo]

rtr(config)#ntp master

Avoid using this command.

[Michal Rzepecki]

why you suggest to avoid using "ntp master" command?

[Leo Laohoo]

Cisco has recommend to avoid using "ntp master" because it tends to confuse peers.

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