different answers from google's authoritative servers

Sotiris Tsimbonis stsimb at forthnet.gr
Wed Jun 1 12:47:13 UTC 2016


On 1/6/16 15:30, Kevin Kretz wrote:
> There's also no reason to assume that the different responses have
> anything to do with the client network.  They could, of course (with
> views), but that you get different responses from the same/similar IP
> is, again, not anything wrong.
> 

True, so below is probably the visualisation of load balancing ... which
most of the times gives me "the wrong logical answer".

[root at syz3ns03 ~]# while true ; do sleep 0.1 ; echo "$(date) $(dig
+short A www.google.com. @ns3.google.com.)" ; done
...
Wed Jun  1 15:42:31 EEST 2016 172.217.16.36
Wed Jun  1 15:42:32 EEST 2016 172.217.16.36
Wed Jun  1 15:42:32 EEST 2016 172.217.16.36
Wed Jun  1 15:42:32 EEST 2016 216.58.208.100
Wed Jun  1 15:42:32 EEST 2016 172.217.16.36
Wed Jun  1 15:42:32 EEST 2016 172.217.16.36
Wed Jun  1 15:42:32 EEST 2016 172.217.16.36
Wed Jun  1 15:42:33 EEST 2016 172.217.16.36
Wed Jun  1 15:42:33 EEST 2016 216.58.208.100
Wed Jun  1 15:42:33 EEST 2016 172.217.16.36
Wed Jun  1 15:42:33 EEST 2016 172.217.16.36
Wed Jun  1 15:42:33 EEST 2016 172.217.16.36
Wed Jun  1 15:42:33 EEST 2016 172.217.16.36
Wed Jun  1 15:42:34 EEST 2016 172.217.16.36
Wed Jun  1 15:42:34 EEST 2016 172.217.16.36
Wed Jun  1 15:42:34 EEST 2016 172.217.16.36
Wed Jun  1 15:42:34 EEST 2016 216.58.208.100
Wed Jun  1 15:42:34 EEST 2016 172.217.16.36
Wed Jun  1 15:42:34 EEST 2016 172.217.16.36
Wed Jun  1 15:42:35 EEST 2016 172.217.16.36
...

So what I'm really trying to find out is if there's anything from my
side to influence the load balancer's decision..

Sot.

> ------------------------------------------------------------------------
> *From: *"Sotiris Tsimbonis" <stsimb at forthnet.gr>
> *To: *"Kevin Kretz" <kevin at rentec.com>
> *Cc: *bind-users at isc.org
> *Sent: *Wednesday, June 1, 2016 8:20:54 AM
> *Subject: *Re: different answers from google's authoritative servers
> 
> On 1/6/16 15:08, Kevin Kretz wrote:
>> Whether the responses to the query work properly in the browsers is a
>> different issue.  There's nothing inherently wrong with multiple and
>> different responses to queries in different subnets or regions.
>>
> 
> True. But I'm trying to figure out why do the answers differ so much,
> when from my side everything is on the same subnet, announced as
> 84.205.252.0/23 on our BGP. I would expect all of them to end up on the
> same google anycast cluster and receive the same answer (or nearly the
> same).
> 
> Sot.
> 
>> ------------------------------------------------------------------------
>> *From: *"Sotiris Tsimbonis" <stsimb at forthnet.gr>
>> *To: *"Kevin Kretz" <kevin at rentec.com>
>> *Cc: *bind-users at isc.org
>> *Sent: *Wednesday, June 1, 2016 7:46:38 AM
>> *Subject: *Re: different answers from google's authoritative servers
>>
>> On 1/6/16 14:41, Kevin Kretz wrote:
>>> Sotiris,
>>>
>>> There could be multiple A records for load balancing.
>>>
>>
>> Of course, but answers of the first and second servers are on the same
>> subnet, and more importantly, work on the users' browsers.
>>
>> The third set of answers is on a completely different subnet and
>> produces ssl errors in the browsers.. Like if it's a cluster for another
>> service, region or whatever..
>>
>> Sot.
>>
>>> ------------------------------------------------------------------------
>>> *From: *"Sotiris Tsimbonis" <stsimb at forthnet.gr>
>>> *To: *bind-users at isc.org
>>> *Sent: *Wednesday, June 1, 2016 7:34:00 AM
>>> *Subject: *different answers from google's authoritative servers
>>>
>>> Hi all,
>>>
>>> We have 3 recursive resolvers on the same subnet, and one of them is
>>> getting different answers for the same things from google's
>>> authoritative dns servers.
>>>
>>> [root at syz3ns01 ~]# RESOLVERS="ns1.google.com. ns2.google.com.
>>> ns3.google.com. ns4.google.com."
>>> [root at syz3ns01 ~]# SITES="www.google.com. www.google.gr."
>>> [root at syz3ns01 ~]# for resolver in ${RESOLVERS} ; do for site in
>>> ${SITES}; do echo "${resolver} ${site} $(dig +short A ${site}
>>> @${resolver})" ; done ; done
>>> ns1.google.com. www.google.com. 216.58.211.4
>>> ns1.google.com. www.google.gr. 216.58.211.3
>>> ns2.google.com. www.google.com. 216.58.211.4
>>> ns2.google.com. www.google.gr. 216.58.211.3
>>> ns3.google.com. www.google.com. 216.58.211.4
>>> ns3.google.com. www.google.gr. 216.58.211.3
>>> ns4.google.com. www.google.com. 216.58.211.4
>>> ns4.google.com. www.google.gr. 216.58.211.3
>>>
>>> [root at syz3ns02 ~]# RESOLVERS="ns1.google.com. ns2.google.com.
>>> ns3.google.com. ns4.google.com."
>>> [root at syz3ns02 ~]# SITES="www.google.com. www.google.gr."
>>> [root at syz3ns02 ~]# for resolver in ${RESOLVERS} ; do for site in
>>> ${SITES}; do echo "${resolver} ${site} $(dig +short A ${site}
>>> @${resolver})" ; done ; done
>>> ns1.google.com. www.google.com. 216.58.211.36
>>> ns1.google.com. www.google.gr. 216.58.211.35
>>> ns2.google.com. www.google.com. 216.58.211.36
>>> ns2.google.com. www.google.gr. 216.58.211.35
>>> ns3.google.com. www.google.com. 216.58.211.36
>>> ns3.google.com. www.google.gr. 216.58.211.35
>>> ns4.google.com. www.google.com. 216.58.211.36
>>> ns4.google.com. www.google.gr. 216.58.211.35
>>>
>>> [root at syz3ns03 ~]# RESOLVERS="ns1.google.com. ns2.google.com.
>>> ns3.google.com. ns4.google.com."
>>> [root at syz3ns03 ~]# SITES="www.google.com. www.google.gr."
>>> [root at syz3ns03 ~]# for resolver in ${RESOLVERS} ; do for site in
>>> ${SITES}; do echo "${resolver} ${site} $(dig +short A ${site}
>>> @${resolver})" ; done ; done
>>> ns1.google.com. www.google.com. 172.217.16.36
>>> ns1.google.com. www.google.gr. 172.217.16.35
>>> ns2.google.com. www.google.com. 172.217.16.36
>>> ns2.google.com. www.google.gr. 172.217.16.35
>>> ns3.google.com. www.google.com. 172.217.16.36
>>> ns3.google.com. www.google.gr. 172.217.16.35
>>> ns4.google.com. www.google.com. 172.217.16.36
>>> ns4.google.com. www.google.gr. 172.217.16.35
>>>
>>> The IP addresses of our servers are 84.205.252.16, 84.205.252.18 and
>>> 84.205.252.20 respectively.
>>>
>>> The problem with the third answer set is on the users' browsers, it
>>> produces an ssl certificate error and users cannot access google.
>>>
>>> traceroute to google's dns servers are different on the penultimate hop
>>> (hop 12)
>>>
>>> [root at syz3ns01 ~]# traceroute ns3.google.com.
>>> traceroute to ns3.google.com (216.239.36.10), 30 hops max, 38 byte
> packets
>>>  1  syz3fw01-dmz.servers.n3.syzefxis.gov.gr (10.95.1.1)  0.405 ms  0.262
>>> ms  0.217 ms
>>>  2  84.205.252.6 (84.205.252.6)  0.718 ms  0.504 ms  0.511 ms
>>>  3  193.92.42.169 (193.92.42.169)  0.937 ms  1.024 ms  0.482 ms
>>>  4  194.219.208.29 (194.219.208.29)  1.017 ms  1.004 ms  0.946 ms
>>>      MPLS Label=757472 CoS=5 TTL=1 S=0
>>>  5  xe-0-3-1.core-lsf-08.forthnet.gr (213.16.247.193)  0.950 ms  1.063
>>> ms  0.982 ms
>>>  6  74.125.48.74 (74.125.48.74)  8.373 ms  8.374 ms  8.341 ms
>>>  7  72.14.237.27 (72.14.237.27)  8.352 ms 72.14.237.189 (72.14.237.189)
>>> 12.085 ms 72.14.237.27 (72.14.237.27)  8.979 ms
>>>  8  209.85.253.114 (209.85.253.114)  26.920 ms  26.114 ms  25.789 ms
>>>      MPLS Label=772454 CoS=5 TTL=1 S=0
>>>  9  216.239.58.8 (216.239.58.8)  50.816 ms 209.85.241.233
>>> (209.85.241.233)  42.159 ms  43.461 ms
>>>      MPLS Label=756878 CoS=5 TTL=1 S=0
>>> 10  209.85.251.178 (209.85.251.178)  45.549 ms  44.474 ms  45.682 ms
>>>      MPLS Label=720256 CoS=5 TTL=1 S=0
>>> 11  74.125.37.103 (74.125.37.103)  39.998 ms 216.239.49.244
>>> (216.239.49.244)  48.116 ms 74.125.37.150 (74.125.37.150)  42.865 ms
>>>      MPLS Label=25186 CoS=5 TTL=1 S=0
>>> 12  209.85.251.231 (209.85.251.231)  39.575 ms 72.14.238.43
>>> (72.14.238.43)  43.933 ms 209.85.242.165 (209.85.242.165)  46.748 ms
>>> 13  * *Icmp checksum is wrong
>>>  *
>>> 14  ns3.google.com (216.239.36.10)  41.453 ms  39.987 ms  47.545 ms
>>> [root at syz3ns01 ~]#
>>>
>>> [root at syz3ns02 ~]# traceroute ns3.google.com.
>>> traceroute to ns3.google.com (216.239.36.10), 30 hops max, 38 byte
> packets
>>>  1  syz3fw01-dmz.servers.n3.syzefxis.gov.gr (10.95.1.1)  0.232 ms  0.283
>>> ms  0.209 ms
>>>  2  84.205.252.6 (84.205.252.6)  0.688 ms  0.535 ms  0.455 ms
>>>  3  193.92.42.169 (193.92.42.169)  1.715 ms  0.835 ms  0.726 ms
>>>  4  194.219.208.29 (194.219.208.29)  1.248 ms  0.876 ms  0.773 ms
>>>      MPLS Label=757472 CoS=5 TTL=1 S=0
>>>  5  xe-0-3-1.core-lsf-08.forthnet.gr (213.16.247.193)  0.755 ms  1.047
>>> ms  0.944 ms
>>>  6  74.125.48.74 (74.125.48.74)  8.331 ms  8.546 ms  8.328 ms
>>>  7  72.14.237.189 (72.14.237.189)  12.286 ms 72.14.237.27 (72.14.237.27)
>>>  5.935 ms 72.14.237.189 (72.14.237.189)  13.211 ms
>>>  8  209.85.253.114 (209.85.253.114)  22.488 ms 209.85.240.160
>>> (209.85.240.160)  25.713 ms  26.401 ms
>>>      MPLS Label=554255 CoS=5 TTL=1 S=0
>>>  9  216.239.57.244 (216.239.57.244)  41.070 ms 209.85.241.233
>>> (209.85.241.233)  34.822 ms 209.85.242.79 (209.85.242.79)  38.180 ms
>>>      MPLS Label=27780 CoS=5 TTL=1 S=0
>>> 10  209.85.251.178 (209.85.251.178)  36.262 ms 66.249.95.39
>>> (66.249.95.39)  44.744 ms 209.85.143.25 (209.85.143.25)  43.497 ms
>>>      MPLS Label=25688 CoS=5 TTL=1 S=0
>>> 11  216.239.49.240 (216.239.49.240)  42.459 ms 216.239.49.244
>>> (216.239.49.244)  42.738 ms  39.587 ms
>>>      MPLS Label=731306 CoS=5 TTL=1 S=0
>>> 12  72.14.238.215 (72.14.238.215)  46.858 ms 216.239.51.147
>>> (216.239.51.147)  48.715 ms 209.85.246.164 (209.85.246.164)  86.761 ms
>>> Icmp checksum is wrong
>>> 13  * * *
>>> 14  ns3.google.com (216.239.36.10)  48.178 ms  48.106 ms  48.157 ms
>>> [root at syz3ns02 ~]#
>>>
>>> [root at syz3ns03 ~]# traceroute ns3.google.com.
>>> traceroute to ns3.google.com (216.239.36.10), 30 hops max, 38 byte
> packets
>>>  1  syz3fw01-dmz.servers.n3.syzefxis.gov.gr (10.95.1.1)  0.297 ms  0.393
>>> ms  0.447 ms
>>>  2  84.205.252.6 (84.205.252.6)  0.454 ms  0.574 ms  0.751 ms
>>>  3  193.92.42.169 (193.92.42.169)  0.938 ms  0.823 ms  0.733 ms
>>>  4  194.219.208.29 (194.219.208.29)  1.260 ms  0.766 ms  1.267 ms
>>>      MPLS Label=757472 CoS=5 TTL=1 S=0
>>>  5  xe-0-3-1.core-lsf-08.forthnet.gr (213.16.247.193)  15.388 ms  1.248
>>> ms  1.446 ms
>>>  6  74.125.48.74 (74.125.48.74)  5.410 ms  5.378 ms  5.435 ms
>>>  7  72.14.237.27 (72.14.237.27)  12.224 ms  12.309 ms 72.14.237.189
>>> (72.14.237.189)  5.354 ms
>>>  8  209.85.240.160 (209.85.240.160)  22.422 ms  35.365 ms  22.601 ms
>>>      MPLS Label=536927 CoS=5 TTL=1 S=0
>>>  9  216.239.57.244 (216.239.57.244)  43.196 ms 209.85.242.79
>>> (209.85.242.79)  40.263 ms 216.239.57.244 (216.239.57.244)  43.387 ms
>>>      MPLS Label=27555 CoS=5 TTL=1 S=0
>>> 10  209.85.251.178 (209.85.251.178)  41.581 ms 209.85.143.25
>>> (209.85.143.25)  36.869 ms 66.249.95.39 (66.249.95.39)  44.804 ms
>>>      MPLS Label=24801 CoS=5 TTL=1 S=0
>>> 11  216.239.49.244 (216.239.49.244)  44.189 ms 74.125.37.154
>>> (74.125.37.154)  47.331 ms 216.239.49.244 (216.239.49.244)  48.582 ms
>>>      MPLS Label=549098 CoS=5 TTL=1 S=0
>>> 12  209.85.246.135 (209.85.246.135)  47.964 ms 209.85.251.231
>>> (209.85.251.231)  42.683 ms 72.14.238.215 (72.14.238.215)  43.525 ms
>>> 13  * * *
>>> 14  ns3.google.com (216.239.36.10)  49.559 ms  48.009 ms  48.148 ms
>>> [root at syz3ns03 ~]#
>>>
>>> Any ideas please?
>>> Sot.
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