Re: Setting up NTP for multicast client service

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james edwards wrote:

> On 8/12/06, *Philip Prindeville* <philipp_subx@xxxxxxxxxxxxxxxxxxxxx
> <mailto:philipp_subx@xxxxxxxxxxxxxxxxxxxxx>> wrote:
>
>
>     Ok, well, so I can be sure that it's the broken build and not my
>     config,
>     what
>     should the config look like ideally?
>
>     -Philip
>
>
>
> If the router that is offering multicast NTP time service has an IP of
> 10.1.2.3 <http://10.1.2.3>
> this would be the minimum config for a client. You may have to define
> the source
> interface for NTP on a Cisco router:
>
> multicastclient
> restrict default ignore
> restrict 224.0.1.1 <http://224.0.1.1>
> restrict 10.1.2.3 <http://10.1.2.3>
> server 127.127.1.0 <http://127.127.1.0>              # local clock (LCL)
> fudge  127.127.1.0 <http://127.127.1.0> stratum 10   # LCL is
> unsynchdronized
> driftfile /etc/ntp/drift
>
>
> I think it is easier to debug this by commenting out all "restrict"
> lines and seeing if it works.
> If it does, your problems are with the ACL's. If it does not work the
> problem is elsewhere.
>
> The lines for "server 127.127.1.0 <http://127.127.1.0>" and "fudge 
> 127.127.1.0 <http://127.127.1.0> stratum 10" allow NTP to take its
> time from localhost, if outside sources cannot be queried.
> /etc/ntp/ needs to be writable by user ntp. In RH's ntpd, ntpd drops
> to user ntp after it starts. I find this file is often owned by root
> in RH, so you will never get a drift file written and long term time
> keeping will not be that good.
>
> NTPd requites 4 separate sources for time so its "false ticker"
> algorithms will operate, allowing one source to go bad. 3 sources are
> required to offer long term accurate time.
>

I tried pretty much this configuration, but something weird happened.

It "discovered" the existence of the NTP server from the multicast packets,
but ends up unicasting to the server (which defeats the purpose of having
multicast set up):

tcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size 512 bytes
08:27:35.875574 IP (tos 0x10, ttl  64, id 4480, offset 0, flags [DF], proto 17, length: 76) 192.168.1.5.ntp > 192.168.1.1.ntp: NTPv3, length 48
        Client, Leap indicator:  (0), Stratum 3, poll 7s, precision -20
        Root Delay: 0.127807, Root dispersion: 0.016067, Reference-ID: 192.168.1.1
          Reference Timestamp:  3364727190.756054997 (2006/08/16 08:26:30)
          Originator Timestamp: 3364727194.896906495 (2006/08/16 08:26:34)
          Receive Timestamp:    3364727194.897505998 (2006/08/16 08:26:34)
          Transmit Timestamp:   3364727255.875508010 (2006/08/16 08:27:35)
            Originator - Receive Timestamp:  +0.000599513
            Originator - Transmit Timestamp: +60.978601515
08:27:35.876638 IP (tos 0xc0, ttl 255, id 0, offset 0, flags [none], proto 17, length: 76) 192.168.1.1.ntp > 192.168.1.5.ntp: NTPv3, length 48
        Server, Leap indicator:  (0), Stratum 2, poll 7s, precision -16
        Root Delay: 0.126724, Root dispersion: 0.005096, Reference-ID: 192.5.41.40
          Reference Timestamp:  3364726610.185859486 (2006/08/16 08:16:50)
          Originator Timestamp: 3364727255.875508010 (2006/08/16 08:27:35)
          Receive Timestamp:    3364727255.876114249 (2006/08/16 08:27:35)
          Transmit Timestamp:   3364727255.876136243 (2006/08/16 08:27:35)
            Originator - Receive Timestamp:  +0.000606221
            Originator - Transmit Timestamp: +0.000628215
08:27:38.879714 IP (tos 0xc0, ttl  16, id 0, offset 0, flags [none], proto 17, length: 76) 192.168.1.1.ntp > 224.0.1.1.ntp: NTPv3, length 48
        Broadcast, Leap indicator:  (0), Stratum 2, poll 6s, precision -16
        Root Delay: 0.126724, Root dispersion: 0.005096, Reference-ID: 192.5.41.40
          Reference Timestamp:  3364726610.185859486 (2006/08/16 08:16:50)
          Originator Timestamp: 0.000000000
          Receive Timestamp:    0.000000000
          Transmit Timestamp:   3364727258.879131138 (2006/08/16 08:27:38)
            Originator - Receive Timestamp:  0.000000000
            Originator - Transmit Timestamp: 3364727258.879131138 (2006/08/16 08:27:38)
08:28:38.992387 IP (tos 0x10, ttl  64, id 4481, offset 0, flags [DF], proto 17, length: 76) 192.168.1.5.ntp > 192.168.1.1.ntp: NTPv3, length 48
        Client, Leap indicator:  (0), Stratum 3, poll 7s, precision -20
        Root Delay: 0.127807, Root dispersion: 0.017013, Reference-ID: 192.168.1.1
          Reference Timestamp:  3364727190.756054997 (2006/08/16 08:26:30)
          Originator Timestamp: 3364727258.879131138 (2006/08/16 08:27:38)
          Receive Timestamp:    3364727258.879773974 (2006/08/16 08:27:38)
          Transmit Timestamp:   3364727318.992358028 (2006/08/16 08:28:38)
            Originator - Receive Timestamp:  +0.000642845
            Originator - Transmit Timestamp: +60.113226845
08:28:38.993495 IP (tos 0xc0, ttl 255, id 0, offset 0, flags [none], proto 17, length: 76) 192.168.1.1.ntp > 192.168.1.5.ntp: NTPv3, length 48
        Server, Leap indicator:  (0), Stratum 2, poll 7s, precision -16
        Root Delay: 0.126724, Root dispersion: 0.005096, Reference-ID: 192.5.41.40
          Reference Timestamp:  3364726610.185859486 (2006/08/16 08:16:50)
          Originator Timestamp: 3364727318.992358028 (2006/08/16 08:28:38)
          Receive Timestamp:    3364727318.992972850 (2006/08/16 08:28:38)
          Transmit Timestamp:   3364727318.992994844 (2006/08/16 08:28:38)
            Originator - Receive Timestamp:  +0.000614880
            Originator - Transmit Timestamp: +0.000636874
08:28:42.861957 IP (tos 0xc0, ttl   1, id 0, offset 0, flags [none], proto 17, length: 76) 192.168.1.1.ntp > 224.0.1.1.ntp: NTPv3, length 48
        Broadcast, Leap indicator:  (0), Stratum 2, poll 6s, precision -16
        Root Delay: 0.126724, Root dispersion: 0.005096, Reference-ID: 192.5.41.40
          Reference Timestamp:  3364726610.185859486 (2006/08/16 08:16:50)
          Originator Timestamp: 0.000000000
          Receive Timestamp:    0.000000000
          Transmit Timestamp:   3364727322.861383795 (2006/08/16 08:28:42)
            Originator - Receive Timestamp:  0.000000000
            Originator - Transmit Timestamp: 3364727322.861383795 (2006/08/16 08:28:42)
08:29:44.113365 IP (tos 0x10, ttl  64, id 4482, offset 0, flags [DF], proto 17, length: 76) 192.168.1.5.ntp > 192.168.1.1.ntp: NTPv3, length 48
        Client, Leap indicator:  (0), Stratum 3, poll 7s, precision -20
        Root Delay: 0.127807, Root dispersion: 0.017990, Reference-ID: 192.168.1.1
          Reference Timestamp:  3364727190.756054997 (2006/08/16 08:26:30)
          Originator Timestamp: 3364727322.861383795 (2006/08/16 08:28:42)
          Receive Timestamp:    3364727322.862003028 (2006/08/16 08:28:42)
          Transmit Timestamp:   3364727384.113337002 (2006/08/16 08:29:44)
            Originator - Receive Timestamp:  +0.000619185
            Originator - Transmit Timestamp: +61.251953184
08:29:44.114458 IP (tos 0xc0, ttl 255, id 0, offset 0, flags [none], proto 17, length: 76) 192.168.1.1.ntp > 192.168.1.5.ntp: NTPv3, length 48
        Server, Leap indicator:  (0), Stratum 2, poll 7s, precision -16
        Root Delay: 0.126724, Root dispersion: 0.005096, Reference-ID: 192.5.41.40
          Reference Timestamp:  3364726610.185859486 (2006/08/16 08:16:50)
          Originator Timestamp: 3364727384.113337002 (2006/08/16 08:29:44)
          Receive Timestamp:    3364727384.113937661 (2006/08/16 08:29:44)
          Transmit Timestamp:   3364727384.113959655 (2006/08/16 08:29:44)
            Originator - Receive Timestamp:  +0.000600661
            Originator - Transmit Timestamp: +0.000622655
08:29:46.844234 IP (tos 0xc0, ttl   1, id 0, offset 0, flags [none], proto 17, length: 76) 192.168.1.1.ntp > 224.0.1.1.ntp: NTPv3, length 48
        Broadcast, Leap indicator:  (0), Stratum 2, poll 6s, precision -16
        Root Delay: 0.126724, Root dispersion: 0.005096, Reference-ID: 192.5.41.40
          Reference Timestamp:  3364726610.185859486 (2006/08/16 08:16:50)
          Originator Timestamp: 0.000000000
          Receive Timestamp:    0.000000000
          Transmit Timestamp:   3364727386.843656480 (2006/08/16 08:29:46)
            Originator - Receive Timestamp:  0.000000000
            Originator - Transmit Timestamp: 3364727386.843656480 (2006/08/16 08:29:46)
...



And the config looks like (minus comments):


restrict default nomodify notrap noquery
restrict 127.0.0.1

multicastclient                 # listen on default 224.0.1.1
restrict 224.0.1.1 mask 255.255.255.255 nomodify notrap
restrict 192.168.1.1 mask 255.255.255.255 nomodify notrap

server 127.127.1.0
fudge   127.127.1.0 stratum 10

driftfile /var/lib/ntp/drift
broadcastdelay  0.008

keys            /etc/ntp/keys




>
> james
>  
>


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