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Beginner

NTP loopback commands

Hello everyone,

 

Could someone please offer insight into what is the difference between using these commands:

ntp source loopback 

ntp server IP source loopback.

 

Do I need to use both?

The second cmd uses loopback while sourcing the ntp packets for synchronizing with the ntp server. 

If I use the 1st command do I still need the 2nd one?

 

Thanks!

1 ACCEPTED SOLUTION

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VIP Advisor

Re: NTP loopback commands

Hello


@cherta wrote:

Sorry for not being clearer. I know what the server cmd does...I was just asking from using the loopback perspective.

If I use ntp source loopback cmd does that also mean that for communication with the ntp server, the ntp packets will use loopback as the source address as well?


ntp source xxx is a global command and ntp server xxxx source xxx is interface specific meaning if this specifys a different source interface then the global command then it will use that specific interface as its ntp source

 

ONLY if both source interfaces (global/interface) are the same will they use the same.



kind regards
Paul

Please rate and mark posts accordingly if you have found any of the information provided useful.
It will hopefully assist others with similar issues in the future
9 REPLIES 9
VIP Advisor

Re: NTP loopback commands

ntp server IP source loopback.  - this is the server IP address when you configured as ntp server

 

ntp source loopback - the router to use the loopback as the time source

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Beginner

Re: NTP loopback commands

Sorry for not being clearer. I know what the server cmd does...I was just asking from using the loopback perspective.

If I use ntp source loopback cmd does that also mean that for communication with the ntp server, the ntp packets will use loopback as the source address as well?

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VIP Advisor

Re: NTP loopback commands

yes you are correct.

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VIP Advisor

Re: NTP loopback commands

Hello


@cherta wrote:

Sorry for not being clearer. I know what the server cmd does...I was just asking from using the loopback perspective.

If I use ntp source loopback cmd does that also mean that for communication with the ntp server, the ntp packets will use loopback as the source address as well?


ntp source xxx is a global command and ntp server xxxx source xxx is interface specific meaning if this specifys a different source interface then the global command then it will use that specific interface as its ntp source

 

ONLY if both source interfaces (global/interface) are the same will they use the same.



kind regards
Paul

Please rate and mark posts accordingly if you have found any of the information provided useful.
It will hopefully assist others with similar issues in the future
Beginner

Re: NTP loopback commands

Ok now it makes sense. In my case I need all ntp packets to always use a loopback so I will only use the global command for simplicity.

 

Thanks!

Beginner

Re: NTP loopback commands

I have a follow up question on this if you don't mind..

I understand that the loopback address should be used as a source for originating ntp packets for both the server and the client. However should we also use the server loopback when point a client to the server (i.e ntp server <loopback IP>?

 

Thanks!

VIP Advisor

Re: NTP loopback commands

Hello


@cherta wrote:

I have a follow up question on this if you don't mind..

I understand that the loopback address should be used as a source for originating ntp packets for both the server and the client. However should we also use the server loopback when point a client to the server (i.e ntp server <loopback IP>?

 

Thanks!


No not unless you want to source different interfaces to different ntp server(s) the global command will suffice.



kind regards
Paul

Please rate and mark posts accordingly if you have found any of the information provided useful.
It will hopefully assist others with similar issues in the future
Beginner

Re: NTP loopback commands

You misunderstood my question..

So if I my server config looks like this:

 

ntp master

ntp source loopback1

 

Should I use this on the client:

ntp server <Loopback1 of server>

or

ntp server <vlan IP of the server>

 

Note: Loopback1 of server is reachable from client.

 

VIP Advisor

Re: NTP loopback commands

Client side you can point to Server Loopback address, make sure it has reachability client.

 

ping to loopback from client, then configure as per your requirement.

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