On 6/22/2011 7:26 AM, Eric Yiu wrote:
Hi,
I am using bind9.7.3-P1 with solaris10x86. I notice that
sometimes our bind server will reply servfail when querying
a zone aws.amazon.com <http://aws.amazon.com> which is expiring, while
this
aws.amazon.com <http://aws.amazon.com> only 60sec cache lifetime, eg.
> /usr/local/bin/dig a aws.amazon.com <http://aws.amazon.com>
; <<>> DiG 9.7.3-P1 <<>> a aws.amazon.com <http://aws.amazon.com>
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 26307
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 6, ADDITIONAL: 1
;; QUESTION SECTION:
;aws.amazon.com <http://aws.amazon.com>. IN A
;; ANSWER SECTION:
aws.amazon.com <http://aws.amazon.com>. 1 IN A
72.21.210.163
;; AUTHORITY SECTION:
aws.amazon.com <http://aws.amazon.com>. 6517 IN NS
ns-932.amazon.com <http://ns-932.amazon.com>.
aws.amazon.com <http://aws.amazon.com>. 6517 IN NS
ns-931.amazon.com <http://ns-931.amazon.com>.
aws.amazon.com <http://aws.amazon.com>. 6517 IN NS
ns-912.amazon.com <http://ns-912.amazon.com>.
aws.amazon.com <http://aws.amazon.com>. 6517 IN NS
ns-923.amazon.com <http://ns-923.amazon.com>.
aws.amazon.com <http://aws.amazon.com>. 6517 IN NS
ns-911.amazon.com <http://ns-911.amazon.com>.
aws.amazon.com <http://aws.amazon.com>. 6517 IN NS
ns-921.amazon.com <http://ns-921.amazon.com>.
;; ADDITIONAL SECTION:
ns-911.amazon.com <http://ns-911.amazon.com>. 3108 IN A
207.171.178.13
;; Query time: 0 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Wed Jun 22 18:59:30 2011
;; MSG SIZE rcvd: 190
> /usr/local/bin/dig a aws.amazon.com <http://aws.amazon.com>
; <<>> DiG 9.7.3-P1 <<>> a aws.amazon.com <http://aws.amazon.com>
;; global options: +cmd
;; Got answer:
*;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 20884
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0*
;; QUESTION SECTION:
;aws.amazon.com <http://aws.amazon.com>. IN A
;; Query time: 0 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Wed Jun 22 18:59:31 2011
;; MSG SIZE rcvd: 32
> /usr/local/bin/dig a aws.amazon.com <http://aws.amazon.com>
^[[A
; <<>> DiG 9.7.3-P1 <<>> a aws.amazon.com <http://aws.amazon.com>
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 47970
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 6, ADDITIONAL: 1
;; QUESTION SECTION:
;aws.amazon.com <http://aws.amazon.com>. IN A
;; ANSWER SECTION:
aws.amazon.com <http://aws.amazon.com>. 60 IN
A 72.21.210.163
;; AUTHORITY SECTION:
aws.amazon.com <http://aws.amazon.com>. 6516 IN NS
ns-932.amazon.com <http://ns-932.amazon.com>.
aws.amazon.com <http://aws.amazon.com>. 6516 IN NS
ns-911.amazon.com <http://ns-911.amazon.com>.
aws.amazon.com <http://aws.amazon.com>. 6516 IN NS
ns-912.amazon.com <http://ns-912.amazon.com>.
aws.amazon.com <http://aws.amazon.com>. 6516 IN NS
ns-931.amazon.com <http://ns-931.amazon.com>.
aws.amazon.com <http://aws.amazon.com>. 6516 IN NS
ns-921.amazon.com <http://ns-921.amazon.com>.
aws.amazon.com <http://aws.amazon.com>. 6516 IN NS
ns-923.amazon.com <http://ns-923.amazon.com>.
;; ADDITIONAL SECTION:
ns-911.amazon.com <http://ns-911.amazon.com>. 3107 IN
A 207.171.178.13
;; Query time: 229 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Wed Jun 22 18:59:31 2011
;; MSG SIZE rcvd: 190
I couldn't really see anything that would explain the SERVFAIL. Each of
those "nameservers" appears to be a load-balancer of some sort. When
queried individually for aws.amazon.com/A, they give a diversity of
answers, implying that they are attempting some form of "DNS
geolocation". None of them seem bothered by EDNS0 or DNSSEC stuff (most
likely they're completely oblivious). When queried individually for
aws.amazon.com/NS, all of them except for one return a single NS record
with their own name in the RDATA. The only exception I saw was
ns-912.amazon.com, which returned ns-945.amazon.com. But, I don't think
that's the cause of the SERVFAIL, since ns-945.amazon.com answers
authoritatively for the name, even though it's not one of the delegated
nameservers for the zone.
Time to look at logs, run named in debug mode and/or fire up a packet
tracer and see what's really going on. Possibly something between you
and the amazon.com nameservers is mangling or blocking packets.
- Kevin
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