![]() The router polls its own internal clock, but the clock is never unreachable, and the router never increases the poll interval to more than every 64 seconds. The interesting value here is in the stratum field, which is one less than the configured value, ntp master 7 in this case. When the router is using its own clock as a master clock (using the ntp master command), the output from show ntp associations looks like the following: address ref clock st when poll reach delay offset disp Time 1: Last NTP response was NOT received (lost in network) Time 0: Last eight responses from server were received The table below provides explanations for possible reach field values using the loss of an NTP response packet as an example. ![]() If an NTP response packet is lost, the missing packet is tracked over the next eight NTP update intervals in the reach field. It gives you the status of the last eight NTP messages (eight bits in octal is 377, so you want to see a reach field value of 377). The reach field is a circular bit buffer. However, the key to knowing that NTP is working properly is looking at the value in the reach field. As long as one peer is the master then everything is fine. If there's an asterisk (*) next to a configured peer, then you are synced to this peer and using them as the master clock. Additional details about the output field are explained in the Basic System Management Commands document. It probably will never reach zero since the packet delay between the client and server is never exactly the same, so the client NTP can't ever exactly match its clock with the server's. The offset decreases toward zero over time. The client slows down or speeds up its clock to match the server's time value. The offset field is the calculated offset (in milliseconds) between the client and server time. ![]() As the NTP server and client are better synced and there aren't dropped packets, this number increases to a maximum of 1024. The poll field represents the polling interval (in seconds) between NTP poll packets. * master (synced), # master (unsynced), + selected, - candidate, ~ configured Router# show ntp associationsĪddress ref clock st when poll reach delay offset disp ![]() Below is an example of output, followed by an explanation of certain output fields. Let's first examine the output of the show ntp associations command and then describe in detail the information that this command presents. Understanding the show ntp associations Command Refer to Cisco Technical Tips Conventions for more information on document conventions. This document is not restricted to specific software and hardware versions. There are no specific requirements for this document. This information is meant to supplement the information available in the Cisco IOS ® Command Reference for the show ntp associations command. There is a considerable amount of information in the output, including packet loss information. This document explains how to use the show ntp associations command output to determine if NTP is working and communicating properly. On Cisco routers, you can use the show ntp associations command to see the status of NTP peerings. You can use Network Timing Protocol (NTP) to synchronize time and clocks across network connections.
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