Cisco router as NTP Server

jahanzaib amin · ‎12-03-2013

Dear Experts,

I am configuring Cisco router as na NTP Server and for this I use below configuration command: But in NTP association it is not replicating the IP address for the NTP. Please suggest how we can solve this issue.

Router #sh run | s ntp

ntp source GigabitEthernet0/0

ntp master 1

ntp update-calendar

Router #sh clock

11:27:15.947 GMT+3 Thu Nov 28 2013

Router #sho clock detail

11:01:01.282 DWPTEC Thu Nov 28 2013

Time source is NTP

Router #show calendar

10:57:56 DWPTEC Thu Nov 28 2013

Router #sh ntp associations

address ref clock st when poll reach delay offset disp

*~127.127.1.1 .LOCL. 0 5 16 377 0.000 0.000 0.232

* sys.peer, # selected, + candidate, - outlyer, x falseticker, ~ configured

Thanks,

Jehan

Peter Paluch · ‎12-04-2013

Jehan,

The 127.127.1.1 address you see in the show ntp associations simply says that the router is using its own internal clock as the time source. Do not worry about it, it is the correct behavior.

In addition, the ntp source GigabitEthernet0/0 command changes the source address of NTP requests if sent out from this router. However, this router is not configured to send any NTP requests - it considers itself to be the clock master - and it only replies to requests from other NTP clients, so this command has no effect.

Best regards,

Peter

jahanzaib amin · ‎12-04-2013

Hello Peter,

So how we can configure this router so it wills send the NTP Clock setting to other devices? I want to use this Router as NTP Server so the Call manager get update time setting from it.

The router Gigabit Interface0/0 has 172.16.7.2 ip address. So on Cisco Call Manager Side I configure this 172.16.7.2 as NTP Source address.

Please suggest that the router can send NTP setting to other Devices.

Thanks,

Jehan

Peter Paluch · ‎12-04-2013

Hi Jehan,

The router is already configured properly to share its time with other devices. In fact, all it requires is using the ntp master command - all other are not necessary. Other devices in your network can use any IP address of this router as their NTP server address, and it will work just nicely. So if your Gi0/0 has 172.16.7.2, use that IP address as the NTP server setting on the other devices. I suggest removing and not using the ntp source command. This command is not necessary nor useful in your current setup, neither on the NTP server, nor on NTP clients. Simply don't worry about it

Best regards,

Peter

jahanzaib amin · ‎12-04-2013

Hello Peter,

I applied below command:

Router #sh run | s ntp

ntp source GigabitEthernet0/0

ntp master 1

ntp update-calendar

So I should remote the NTP Source? and apply this way?

Router #sh run | s ntp

ntp master 1

ntp update-calendar

Thanks,

Jehan

Peter Paluch · ‎12-04-2013

Hi Jehan,

So I should remote the NTP Source? and apply this way?

Router #sh run | s ntp

ntp master 1

ntp update-calendar

Yes, exactly.

By the way, do you really want the router to be the NTP time source for your network? These routers do not have particularly high precision clock, so when they start drifting, the whole network will drift along. More often, a standalone server (either Linux or Windows) is used as an NTP source server, possibly even syncing its own time with external time servers out on the internet.

Best regards,

Peter

jahanzaib amin · ‎12-04-2013

Hi,

Do after do below config

Router #sh run | s ntp

ntp master 1

ntp update-calendar

The NTP associate will replicate the IP for the Gigabit Interface or it will show the same result for NTP Associate ?

Router #sh ntp associations

address ref clock st when poll reach delay offset disp

*~127.127.1.1 .LOCL. 0 5 16 377 0.000 0.000 0.232

* sys.peer, # selected, + candidate, - outlyer, x falseticker, ~ configured

Peter Paluch · ‎12-04-2013

Jehan,

The NTP associate will replicate the IP for the Gigabit Interface or it will show the same result for NTP Associate ?

The output of the show ntp associations on your NTP master will not change. This output is not really relevant for you: it always tells you what time source the device is using. An NTP master uses its own clock as the time source, and this is what the command tells you. The show ntp associations would be more interesting on the NTP clients taking their time from this router.

Best regards,

Peter

jahanzaib amin · ‎12-04-2013

Hello,

So you mean we can test the NTP Server setting this way that we make another rotuer as Client and do NTP associte command and see the output.... In this case on the Client side it will show the IP of Gigbait interface ?

Jehan

Peter Paluch · ‎12-04-2013

Jehan,

So you mean we can test the NTP Server setting this way that we make  another rotuer as Client and do NTP associte command and see the output

Yes. If you want to make another router a client that make sure that you first manually set the time on the client router to be similar to the time on the NTP master. Big differences in time between the NTP server and clients are handled very slowly by NTP - the sync could take hours.

In this case on the Client side it will show the IP of Gigbait interface ?

You will see the address used in the ntp server command on the client. It is not necessarily the address of the Gig0/0 interface if you have configured a different IP address as the server's address on the client.

Best regards,

Peter