NTP

Hi All,

   I was working on one of the lab requirements based on NTP and have few
questions on the same.The lab requirement ask R3 to take clock from BB3 and
R6 to take clock from BB1.Also ask to R3 and R6 peer each other to get clock
if there respective BB clock goesaway.I used the below configuration on R3
and R6

R3

ntp server <bb3 ip address>
ntp peer <r6 ip address>

R6

ntp server <bb1 ip address>
ntp peer <r3 ip address>

BBs are giving Stratum 5 clock and so I as assuming both R3 and R6 should
see BBs as the preferred server.Is this understanding right ? The actual
result which I obtained was on R3,it sees the R6 as preferred clock server
and even it doesn't keep the BB3 server as selected backup.So I removed the
ntp peer statement on R3 to R6 and found the R3 takes the BB3 clock as
server and gets synchronised.So I added back again the ntp peer statement on
R3 and found again R3 choosing the R6 and ignoring BB3.I ran debug based on
NTP and found the below messages

Mar 1 04:18:37.119: NTP: nlist 3, allow 0, found 3, low -7.964615, high
7.962570
Mar 1 04:18:37.119: *NTP: 204.12.1.254 discarded, outlier*
Mar 1 04:18:37.119: NTP: candidate 183.1.46.6 cdist 87.963593 error
7.893570
Mar 1 04:18:37.119: NTP: candidate 150.1.6.6 cdist 95.960403 error
15.891159
Mar 1 04:18:37.119: NTP: survivor 183.1.46.6 offset -0.001007, cdist
87.96359
Mar 1 04:18:37.119: NTP: survivor 150.1.6.6 offset -0.001109, cdist
95.96040
Mar 1 04:18:37.123: NTP: synced to new peer 183.1.46.6

It gave message as outlier and tried to understand what is that mean ,my
understanding was that if the clock offset is too high when compared to
other peers,it may ignore the one which have high offset.I am not sure
whether I understood right .Kindly correct me if I am wrong in that.Assuming
my understanding on that is right,is not always the high stratum clock wins
?.Does this means it compars the offset before comparing the startum clock.I
am sure missing some basic on NTP.

How to make in this scenario,R3 prefering BB clock and not the R6 even
though the offset for BB clock is comparitvely higher.

Thanks for the assistance.

Regards
Anantha Subramanian Natarajan

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Received on Mon Jul 06 2009 - 12:33:17 ART