Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

ntp sync

After configuring the following, unable to sync time with the ntp server. Please correct me if I'm missing something. NTP is well reachanble from the devices.


service timestamps debug datetime msec localtime show-timezone

service timestamps log datetime msec localtime show-timezone

clock timezone IST 5 30

ntp source Loopback0

ntp server

ntp server



Cisco Employee

Re: ntp sync

The config looks okay. Are you sure the NTP server has a route back to the device's loopback IP address? You can enable debug ntp packets, debug ntp events, and debug ntp sync to get a better idea of what is going on. You could also get a sniffer, and filter on all 123/udp packets to make sure the NTP request is making it to the servers, and then back to the device.

Hall of Fame Super Silver

Re: ntp sync


There are several things that might produce the symptoms that you describe. The first thing that I would check is IP connectivity. I know that your post indicates that the NTP servers are well reachable, but I would ask you to do this: do an extended ping to the address of one of the servers and in the extended commands of the extended ping specify the source address as the loopback of your local router. It is not just a question of having a route to the server address it is a question of the server having a route back to your source address.

Another thing to check for is the possibility that the server is configured wiht an access list which controls addresses to which it will respond. Since the server addresses are in 10 address space it implies that the servers are within your enterprise network and so hopefully this information is available to you.

Another possibility is that there might be an access list on one of the routers or on some router along the path that is denying the NTP packets.

One thing that you could do that might be helpful is to post the output of show ntp association detail. This will give us some information about the configured servers.