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Forum Replies

  1. Hello Guy!

    The first complete specification of NTP, that is, Version 1, appeared in 1988 (RFC 1059) which provided simple symmetric and client server mode operation.

    Version 2 appeared in 1989 (RFC 1119) and added symmetric key authentication using DES-CBC.

    Version 3, which is the version that is most used today was first described in 1992 (RFC 1305) and has been systematically improved over the years. It introduced formal correctness principles, revised algorithms and broadcast mode . This is the default version that is available in most Cisco devices using

    ... Continue reading in our forum

  2. Hello Laz,
    A few questions.

    1. Let’s say I have a router that is configured to receive the ntp information from a ntp server located in the internet. I have also configured the time locally by using clock set command. Which time will have more preference? In another words, which time the router will use?
    2. What is the command to change time-zone in a router?
    3. Let’s say a router is configured to sync its time from a ntp server and the ntp server is feeding UTC time to the router. However, I like the router to show EST time in the clock or let’s say in syslog message
    ... Continue reading in our forum

  3. Hello AZM

    **Question 1**
    When NTP is configured on a device, there is what is called a poll interval. This interval is dynamic and as client and server become better synced, and there aren’t any dropped packets, this interval increases to a maximum of 1024 seconds. If you change the time using the clock set command, the time you set will become the new time. However, when the poll interval is exhausted, the device will re-sync with the NTP server. So any changes you make manually will be over-ridden at the next poll interval.

    **Question 2**
    To change the ti

    ... Continue reading in our forum

  4. Hi Sreenath,

    NTP and PTP have some similarities. NTP is the most common protocol to sync clocks on your network, that’s what you will mostly see on networks nowadays. We use it to sync the clock on network devices but also computers/servers etc. NTP uses software timestamping and supports millisecond synchronization.

    PTP is similar to NTP but uses hardware timestamping and offers nanosecond or picosecond-level synchronization.

    For 99% of the devices, NTP is good enough but if you have devices where millisecond-level synchronization is not good enough, PTP is an

    ... Continue reading in our forum

  5. Hello Kevin,

    NTP authentication can be confusing. With your configuration, no authentication occurs because the client isn’t configured for authentication. I did a quick lab with your configuration.

    The server will send “regular” NTP packets without an MD5 hash. Once you change the ntp server command on the client, it works.

    Before:

    https://www.cloudshark.org/captures/c40ea3a2748b

    After:

    Client(config)#ntp server 192.168.1.1 key 1

    https://www.cloudshark.org/captures/e016b1c2e8a8

    Once the client wants to use authentication, the server responds with the same MD5

    ... Continue reading in our forum

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