Hi,
we run our servers in ~30 datacenters around the world and we recently
came across a strange issue in Mexico. From time to time (like twice a
day), the {1,2,3,4}.centos.ntp.org domains returns just one IP instead
of usual 4. Moreover, that IP does not provide NTP service or is
completely down.
The issue does not appear at any of our other DCs, so BGP and/or DNS
GeoBalancing may be involved.
The dig +trace output from the time the issue occurs is attached below.
The issue usually lasts around 20minutes. If ntpd is restarted during
this time, it won't work (as version of ntpd distributed with CentOS 6
does resolving only during startup).
I tried to fire a bug against Centos [1], but it appeared that it is
actually somebody from ntp.org responsible for DNS infrastructure.
Could you please have a look or direct me to the responsible party?
Regards
Jiri Horky
[1] https://bugs.centos.org/view.php?id=9680
-------------------
Sat 31 Oct 2015 06:52:21 AM CET
; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.37.rc1.el6_7.4 <<>> +trace
1.centos.pool.ntp.org
;; global options: +cmd
. 518400 IN NS k.root-servers.net.
. 518400 IN NS g.root-servers.net.
. 518400 IN NS l.root-servers.net.
. 518400 IN NS i.root-servers.net.
. 518400 IN NS a.root-servers.net.
. 518400 IN NS b.root-servers.net.
. 518400 IN NS d.root-servers.net.
. 518400 IN NS c.root-servers.net.
. 518400 IN NS m.root-servers.net.
. 518400 IN NS e.root-servers.net.
. 518400 IN NS j.root-servers.net.
. 518400 IN NS f.root-servers.net.
. 518400 IN NS h.root-servers.net.
;; Received 496 bytes from 127.0.0.1#53(127.0.0.1) in 1 ms
org. 172800 IN NS d0.org.afilias-nst.org.
org. 172800 IN NS b2.org.afilias-nst.org.
org. 172800 IN NS b0.org.afilias-nst.org.
org. 172800 IN NS c0.org.afilias-nst.info.
org. 172800 IN NS a2.org.afilias-nst.info.
org. 172800 IN NS a0.org.afilias-nst.info.
;; Received 441 bytes from 192.58.128.30#53(192.58.128.30) in 25 ms
ntp.org. 86400 IN NS ns2.ntp.org.
ntp.org. 86400 IN NS ns1.ntp.org.
ntp.org. 86400 IN NS dns2.udel.edu.
ntp.org. 86400 IN NS dns1.udel.edu.
;; Received 153 bytes from 199.19.56.1#53(199.19.56.1) in 194 ms
pool.ntp.org. 3600 IN NS f.ntpns.org.
pool.ntp.org. 3600 IN NS h.ntpns.org.
pool.ntp.org. 3600 IN NS e.ntpns.org.
pool.ntp.org. 3600 IN NS i.ntpns.org.
pool.ntp.org. 3600 IN NS b.ntpns.org.
pool.ntp.org. 3600 IN NS c.ntpns.org.
pool.ntp.org. 3600 IN NS g.ntpns.org.
pool.ntp.org. 3600 IN NS d.ntpns.org.
pool.ntp.org. 3600 IN NS a.ntpns.org.
;; Received 189 bytes from 149.20.68.4#53(149.20.68.4) in 138 ms
1.centos.pool.ntp.org. 150 IN A 132.248.30.3
;; Received 76 bytes from 174.127.124.192#53(174.127.124.192) in 50 ms
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