ntpq command output and unreachable state?

[Omer Faruk Sen]

I have used ntpq -c associations to see if the server is reachable or
not. But even the peers are not reachable my ntpd answers to queries
for some time and after recovering connection (reachable state) my
ntpd doesn't answer to ntp clients even if ntpq -c peers states "*"
state. But after certain amount of time time can be synced with my
ntpd server. (this recovery process took more than 1 hour in my test
setup).



On Sat, Dec 19, 2009 at 2:10 PM, Omer Faruk Sen <omerfsen at gmail.com> wrote:
> Hi,
>
> I am trying to understand output of ntpq -c peers (or ntpq -p). What I
> am trying to understand that when a ntp server is announced as
> unreachable. I have made a test. I setup a test ntp server with
>
>
> /etc/ntp.conf
> =============
> restrict default nomodify notrap noquery
> restrict 127.0.0.1
> server 0.pool.ntp.org
> server clock.isc.org
>
> and started ntpd daemon using
>
> /usr/sbin/ntpd -c /etc/ntp.conf -p /var/run/ntpd.pid -f
> /var/db/ntpd.drift -g -l /var/log/ntpd.log
>
> and blocked all port 123 traffic that goes out from this ntp server at
> my gateway (to simulate to lost connection on ntp servers at ntp.conf)
> After 26 hours later my ntpd still thinks that it can reach to
> "clock.isc.org" (as can be seen with "*" mark before clock.isc.org
> below)
>
> # ntpq -c peers
>     remote           refid      st t when poll reach   delay   offset  jitter
> ==============================================================================
> +194.27.110.130  131.188.3.220    2 u  27h 1024    0   67.816   13.282   0.000
> *clock.isc.org   204.123.2.5      2 u  26h 1024    0  224.461  -15.208   0.000
>
> But I am sure that it can't reach (I sniff my firewall so no traffic
> comes from clock.isc.org). My question is how can I find out that my
> ntp servers defined at ntp.conf are unreachable (I know that if ntp
> server is unreachable than my local ntp server stops to answer for ntp
>  requests)
>
> Best Regards.
>