ntpd Invalid-NAK error

[Miroslav Lachman]

Dan Lukes wrote on 2017/06/13 14:25:

> A na to uz je potreba mit zachyceny pozadavek a odmitnutou odpovedi.
> Celou (tedy u tcpdumpu option -s 1600).

Je tohle ten spravny packet?

tcpdump: listening on nfe0, link-type EN10MB (Ethernet), capture size 
1600 bytes
16:13:45.666221 00:24:73:86:ce:22 > 01:80:c2:00:00:0a, ethertype Unknown 
(0x88a7), length 188:
         0x0000:  0003 0000 01b4 f8bc 0001 000e 0000 0000  ................
         0x0010:  0024 7386 ce09 0007 0026 3343 6f6d 2042  .$s......&3Com.B
         0x0020:  6173 656c 696e 6520 5377 6974 6368 2032  aseline.Switch.2
         0x0030:  3932 382d 5346 5020 506c 7573 000e 0018  928-SFP.Plus....
         0x0040:  352e 3230 2052 656c 6561 7365 2031 3130  5.20.Release.110
         0x0050:  3150 3035 0011 0013 5631 3030 5230 3031  1P05....V100R001
         0x0060:  4230 3344 3030 3200 1000 0731 3136 000c  B03D002....116..
         0x0070:  0014 1100 0000 0000 0000 0000 0000 0000  ................
         0x0080:  0000 0003 000d 3343 6f6d 2032 3932 3800  ......3Com.2928.
         0x0090:  0200 1947 6967 6162 6974 4574 6865 726e  ...GigabitEthern
         0x00a0:  6574 312f 302f 3234 000b 0006 0003       et1/0/24......
16:13:48.662231 IP (tos 0xc0, ttl 255, id 59917, offset 0, flags [none], 
proto UDP (17), length 80)
     192.168.23.253.123 > 192.168.23.2.123: NTPv3, length 52
         Client, Leap indicator: clock unsynchronized (192), Stratum 0 
(unspecified), poll 7 (128s), precision -18
         Root Delay: 0.000000, Root dispersion: 0.000000, Reference-ID: 
(unspec)
           Reference Timestamp:  0.000000000
           Originator Timestamp: 0.000000000
           Receive Timestamp:    0.000000000
           Transmit Timestamp:   3174208156.291851013 (2000/08/02 14:29:16)
             Originator - Receive Timestamp:  0.000000000
             Originator - Transmit Timestamp: 3174208156.291851013 
(2000/08/02 14:29:16)
         Key id: 0

>> server 0.freebsd.pool.ntp.org iburst
>> server 1.freebsd.pool.ntp.org iburst
>> server 2.freebsd.pool.ntp.org iburst
>
> Ja vim, ze jsem paranoidni, ale i tak reknu, ze jsi odvazna skolacka. Ja
> bych asi nebral cas z neznameho zdroje, vybiraneho podle ne prilis
> zrejmych kriterii.

Driv jsem pouzival jeden "znamy bezpecny" zdroj, ale ten uz neni, takze 
rozhodnout se pro nejaky jiny verejny je skoro stejne, jako tam nechat 
tuhle defaultni konfiguraci. Ale jinak mas samozrejme pravdu.

Mirek