different answers from google's authoritative servers

Kevin Kretz kevin at rentec.com
Wed Jun 1 12:08:12 UTC 2016 

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. 


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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