Re: NTP

From: Petr Lapukhov (petr@internetworkexpert.com)
Date: Sun Jul 23 2006 - 12:54:04 ART

Actually, I have never seen ntp peers getting in sync if none of them
have authoriative time source. That is, if you set two routers as
ntp peers, you also need to set up one as ntp master, or let
one (or both) of the routers pull time from ntp server.

The whole idea of NTP, AFAIK, is to propagate authoriative time
reference in loopless (tree-like) topology, with authority being the root.
ntp peering is useful for backup purposes, like when you pull time
from you upstream ISP, and peer with your friendly neighbor, to
save clocks in case you lose your uplink.

HTH

2006/7/23, Faryar Zabihi (fzabihi) <fzabihi@cisco.com>:
>
> So If I want stratum 3 on R4(being one hop from R3) and it R4 should
> sync with R3 I just need
> R4
> Ntp server (r3 IP)
> R3
> Ntp master 2
> ?
> Why does it take 5 mins to sync. When u debug it shows the time from R3
> but it rejects it until it just gives up
>
> Faryar
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com ] On Behalf Of
> Scott Morris
> Sent: Saturday, July 22, 2006 1:08 PM
> To: 'Sami'; 'Cisco certification'
> Subject: RE: NTP
>
> NTP Peers will try to mutually agree on a time (but nobody REALLY knows
> what time it is)
>
> NTP Server will peer with a master. The master has authority (in other
> words it actually knows the time).
>
> HTH,
>
>
> Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713,
> JNCIE #153, CISSP, et al.
> CCSI/JNCI-M/JNCI-J
> IPExpert VP - Curriculum Development
> IPExpert Sr. Technical Instructor
> smorris@ipexpert.com
> http://www.ipexpert.com
>
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Sami
> Sent: Saturday, July 22, 2006 2:02 PM
> To: Cisco certification
> Subject: NTP
>
> Group,
>
> Could some one explian when to use ntp server and ntp peer command...I
> have seen some workgroup solution some time they use ntp server othe
> time they use ntp peer command.
>
> Thanks
>
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-- 
Petr Lapukhov, CCIE #16379
petr@internetworkexpert.com

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