NTP few questions

[sarahr202]

Hi everybody.

Please consider the following output.

ntp_clent#show ntp associations      address         ref clock     st  when  poll reach  delay  offset    disp* 206.191.241.44   128.194.103.14    5     7  8192   76     4.1    0.05   910.5 * master (synced), # master (unsynced), + selected, - candidate, ~ configuredntp_clent#                           

That is the image I have on mind based on the above output.

ntpClient--------------ntpserver(206.191.241.44) at str-5--------ntpserver-str4---ntpserver-str3---nppserver-str2--ntpserver-str1--reference clock.

1)Did I visualize it correctly?

2)The ip address 128.194.103.14 belongs to ntp server directly connected to reference clock right?

3)Delay 4.1 in above output shows the total delay i.e  time request to travel to ntp server and back to ntp client ?

thanks and have a great weekend.

[Reza Sharifi · Accepted solution]

Hi Sarah,

Yes, you are correct an all questions:

NTP uses a stratum to describe how many NTP hops  away that a network device is from an authoritative time source. A  stratum 1 time server has an authoritative time source (such as an  atomic clock) directly attached to the server. A stratum 2 NTP server  receives its time through NTP from a stratum 1 NTP server, which in turn  connects to the authoritative time source.

http://www.cisco.com/en/US/docs/switches/datacenter/nexus1000/sw/4_2_1_s_v_1_4_a/system_management/configuration/guide/n1000v_system_8ntp_external_docbase_0900e4b181ef9988_4container_external_docbase_0900e4b18275f626.html

Also, this document explains each files from "sh ntp asso" command:

http://www.cisco.com/en/US/products/sw/iosswrel/ps1818/products_tech_note09186a008015bb3a.shtml

HTH

[sarahr202]

Thanks Reza.

I am a little confused about the term " peer" used in the forwarded links.

1) Peer association provides redundancy .

2) Can  we establish peer relationship between switch-1 and server-2 using ntp peer command? ( I understand better choice would be to configure sw1 to point to server-2,but just out of curiosity, is it possible)

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I noticed that another link you forwarded uses the term" peer" to refer to ntp server. For e.g

Router#show ntp associations address            ref clock         st      when    poll   reach   delay   offset    disp ~172.31.32.2       172.31.32.1       5       29      1024   377     4.2     -8.59     1.6 +~192.168.13.33    192.168.1.111     3       69      128    377     4.1     3.48      2.3 *~192.168.13.57    192.168.1.111     3       32      128    377     7.9     11.18     3.6 * master (synced), # master (unsynced), + selected, - candidate, ~ configured

If there's an asterisk (*) next to a configured peer, then you are       synced to this peer and using them as the master clock. As long as one peer is       the master then everything is fine.

3)Do we use the word " peer" to mean any ntp server  which the local router/switch uses to synchronize its clock with ? i.e it does not mean there is peer relationship configured between the two using ntp peer IP-ADDRESS command.

thanks for your help and enjoy your weekend.

[Leo Laohoo · Accepted solution]

I haven't seen (for quite awhile) anyone using the "ntp peer" command.  It's always been "ntp server".

Cisco does NOT recommend using "ntp master" as this could tell the appliance to say, "Hey, don't trust anyone else.  I AM the NTP KIIIIIIIIIIIIIIING!" ... even though the time/date is incorrect.