From: Roberto Fernandez (rofernandez@us.telefonica.com)
Date: Tue Jun 13 2006 - 11:01:28 ART
Daniel,
Thank you very much; it makes total sense when seen that way.
It looks to me more philosophical than technical because a stratum level
more or less, doesn't make the difference. But from the hierarchical
design point of view, it is the answer. Being this the line followed by
every lab I've seen, it is the law from now on.
Thanks again,
Roberto
-----Original Message-----
From: Daniel Ramirez [mailto:daniel.ramirezdelamo@gmail.com]
Sent: Tuesday, June 13, 2006 6:02 AM
To: Roberto Fernandez
Cc: Cisco certification
Subject: Re: NTP associacions, help on hidden semantic details
Roberto,
The key point is the stratum level. The stratum architecture defines
the ntp relationship:
+ You must configure "ntp server" when you want to synchronize with a
more reliable time source (i.e. less stratum level). Ntp server => In
this case you request time info to a reliable source
+ You should use "ntp peer" when you want to interact with a time
source of your same stratum level (i.e. same reliability). Ntp peer =>
In this case you request time info & you provide time info to a time
source of the same reliability.
In your example: BB1 & BB3 are more reliable time source => configure
server relation.
R6 & R3 (same level of reliability) =>
configure peer relation.
Best Regards.
D. Ramirez
Network Engineer
Telefonica Data
On 6/12/06, Roberto Fernandez <rofernandez@us.telefonica.com> wrote:
> Friends,
>
> I need your help trying to figure out, where are the key works which
led
> into one direction or the other.
>
>
> The requirements of IEWB Vol 1, Lab 1, Session 9.3 are as follows:
>
> -Configure R3 and R6 to get network time from BB3 and BB1 respectively
> -Configure R1, R2 and SW1 to get network time from R3
> -Configure R4, R5, and SW2 to get network time from R6
> -R3 should fail over and get network time from R6 in the event that
BB3
> becomes unavailable
> -R6 should fail over and get network time from R3 in the event that
BB1
> becomes unavailable
>
>
> Here I see two solutions to fulfill the last two requirements,
>
> 1- The "ntp peer"
> 2- The "ntp server" (taking the precaution of adding the preferred
> keyword to the server commands pointing to BB1 and BB3
>
> Configuration for #1
> --------------------
> R3
> ntp server <BB1 ip address> preferred
> ntp peer <R6 ip address>
>
> R6
> ntp server <BB2 ip address> preferred
>
> Configuration for #2
> --------------------
>
> R3
> ntp server <BB1 ip address> preferred
> ntp server <R6 ip address>
>
> R6
> ntp server <BB2 ip address> preferred
> ntp server <R3 ip address>
>
> The answer key prefers #1 and it also the choice for some other
similar
> questions. Maybe I'm lost on the semantics of the requirement so I'd
> appreciate if someone can point to the keywords which lead to the
right
> solution.
>
> Thanks again
>
>
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