NTP on DDR

Discussion in 'Cisco' started by Groper, Oct 24, 2003.

  1. Groper

    Groper Guest

    I have a central PPP server (3640) and want my remote sites to sync thier
    time when they connect once a day to download files.
    But I don't want NTP to bring the line up itself.

    How would I configure NTP on both sides to sync only when connected.

    Thanks
    Groper
     
    Groper, Oct 24, 2003
    #1
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  2. Groper

    Ivan Ostres Guest

    In interesting traffic access-list deny NTP traffic.

    Ivan
     
    Ivan Ostres, Oct 24, 2003
    #2
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  3. Groper

    Groper Guest

    Interesting idea, just done some further research. What about if I were to
    use

    ppp Server 3640
    !
    Dialer0
    ntp broadcast


    remote 2620
    !
    BRI0/0
    ntp broadcast client

    Would this be better, or should I use a combination of both?

    Thanks
    Groper
     
    Groper, Oct 24, 2003
    #3
  4. Groper

    Groper Guest

    OK, looks like the ntp broadcast keeps bringing the line up, not a desired
    result.

    On the interesting traffic access list, surly if I block ntp, I'll get no
    sync at all

    Thanks
    Groper
     
    Groper, Oct 24, 2003
    #4
  5. Groper

    Ivan Ostres Guest

    You will, interesting traffic access-list is just for bringing line up (and
    keeping it up), but it won't block anything when line is up. Just will
    prevent ntp for bringing line up.

    Ivan
     
    Ivan Ostres, Oct 24, 2003
    #5
  6. You misunderstand. The interesting traffic 'access-list' is only what
    causes dialing. It is unfortunated that it uses a think called
    'access-list.' access-list really is just a data structure to describe a
    group of IP addresses and service ports.

    If you wanted to stop NTP traffic, you would need to add an "access-GROUP"
    to the interface. "dialer-group" only controls dialing. So deny NTP only
    on the dialer-group access list but not the access-group access list.
     
    Phillip Remaker, Oct 24, 2003
    #6
  7. So make it uninteresting then.
    You're not blocking the traffic when you make it uninteresting, you're
    just telling the router to not bring/keep the link up on account of these
    particular packets.

    The traffic itself is still forwarded across the link.
     
    Martin Gallagher, Oct 24, 2003
    #7
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