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palehorse
Asked: 2016-08-24 09:41:41 +0800 CST

How to troubleshoot name resolution SERVFAIL for a single host

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I have a server running CentOS 6 with Bind 9.8.2 which is not resolving DNS for 1 particular host which isn't even one of the zones that this server hosts. All other querys work fine, including querys for other hosts in the domain that I'm having issue with.

From the problem server

$ dig www.example.com

; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.47.rc1.el6 <<>> www.example.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 6139
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;www.example.com.             IN      A

$ nslookup -debug www.example.com
Server:         x.x.x.x
Address:        x.x.x.x#53

------------
    QUESTIONS:
        www.example.com, type = A, class = IN
    ANSWERS:
    AUTHORITY RECORDS:
    ADDITIONAL RECORDS:
------------
** server can't find www.example.com: SERVFAIL
Server:         x.x.x.x
Address:        x.x.x.x#53

$ dig en-es.example.com

; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.47.rc1.el6 <<>> en-es.example.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 4755
;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 4, ADDITIONAL: 1

;; QUESTION SECTION:
;en-es.example.com.           IN      A

;; ANSWER SECTION:
en-es.example.com.    600     IN      A z.z.z.z

From other servers (both on the same network and outside)

$ dig www.example.com

; <<>> DiG 9.9.4-RedHat-9.9.4-29.el7_2.3 <<>> www.example.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 58315
;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;www.example.com.             IN      A

;; ANSWER SECTION:
www.example.com.      324     IN      CNAME   my.cname.net.
my.cname.net        . 20      IN      A       y.y.y.y

How do I track down why this query results in a SERVFAIL allowing the next logical step, fixing the issue.

bind centos6

1 Answers

  1. Best Answer

    The problem was solved today, it turns out it was an issue with the zone files for the domain in question. Apparently the client had modifications which involved what they called "containers" (assuming it was zone delegation) and after some DNS health checks some odd errors were returned. They reversed their changes an everything went back to normal. It seems they had delegated the subdomain www but had not added the records needed proper authority. I believe it caused some sort of DNSSEC issue that our server would not resolve.

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