Different handling of referrals by dig and nslookup
kalpesh varyani
kalpesh.link at gmail.com
Sat Feb 13 17:07:03 UTC 2010
Hi all,
I have named 9.4.3-P3 running on 2 linux systems(A & B).
A has recursion disabled and the B has recursion enabled.
>From a third linux system, I try name resolution using dig or nslookup.
In this system, I have resolv.conf as:
nameserver A
nameserver B
When I try to resolve names, using dig (with +notrace) and ping, I observe
that both these utilites, upon getting a referral discontinues the
resolution process.
# dig foo.example.com.
; <<>> DiG 9.3.2 <<>> foo.example.com.
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 1004
;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 13, ADDITIONAL: 0
;; QUESTION SECTION:
;foo.example.com. IN A
;; AUTHORITY SECTION:
. 83311 IN NS e.root-servers.net.
. 83311 IN NS f.root-servers.net.
. 83311 IN NS g.root-servers.net.
. 83311 IN NS h.root-servers.net.
. 83311 IN NS i.root-servers.net.
. 83311 IN NS j.root-servers.net.
. 83311 IN NS k.root-servers.net.
. 83311 IN NS l.root-servers.net.
. 83311 IN NS m.root-servers.net.
. 83311 IN NS a.root-servers.net.
. 83311 IN NS b.root-servers.net.
. 83311 IN NS c.root-servers.net.
. 83311 IN NS d.root-servers.net.
;; Query time: 4 msec
;; SERVER: xx.xxx.xxx.xxx#53(xx.xxx.xxx.xxx)
;; WHEN: Sat Feb 13 21:09:39 2010
;; MSG SIZE rcvd: 244
#
That is, when name server A returns a referral, dig & ping donot try to
query the name server, i.e. B, specified in resolv.conf.
But, when I use nslookup, I see that it whenever it gets a referral, it
queries the next name server specified in resolv.conf.
This is a desired behaviour as nslookup has nofail option as default
(specified in the man page of nslookup).
I would like have "ping" querying the next name sever in the event of
receiving a referral from the first name sever.
Can anyone suggest whether this is feature is really not supported in dig
and ping?
Thanks in advance!
Regards,
Kalpesh.
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