Choosing authoritative nameservers
Elias
elias at streamyx.com
Wed Jun 2 08:20:38 UTC 2010
Hi guys,
Does anyone know how BIND chooses which authoritative server to refer to?
When a referal returns ns1.abc.com, ns2.abc.com and ns3.abc.com, will the
recursive server randomly send out a request to either ns1, ns2 or ns3 or is
there a selection algorithm?
I've got a problem resolving www.klse.com.my and its probably caused by a
broken server along the path. But the problem is I keep hitting the same
server everytime no matter how many times I flush my caches.
# /usr/local/bin/dig www.klse.com.my +trace
; <<>> DiG 9.7.0 <<>> www.klse.com.my +trace
;; global options: +cmd
. 491578 IN NS c.root-servers.net.
. 491578 IN NS f.root-servers.net.
. 491578 IN NS m.root-servers.net.
. 491578 IN NS j.root-servers.net.
. 491578 IN NS i.root-servers.net.
. 491578 IN NS k.root-servers.net.
. 491578 IN NS d.root-servers.net.
. 491578 IN NS g.root-servers.net.
. 491578 IN NS h.root-servers.net.
. 491578 IN NS a.root-servers.net.
. 491578 IN NS l.root-servers.net.
. 491578 IN NS b.root-servers.net.
. 491578 IN NS e.root-servers.net.
;; Received 504 bytes from 192.168.10.209#53(192.168.10.209) in 13 ms
my. 172800 IN NS dns2.mynic.net.my.
my. 172800 IN NS ns.uu.net.
my. 172800 IN NS ns5.jaring.my.
my. 172800 IN NS ns2.cuhk.edu.hk.
my. 172800 IN NS ns6.jaring.my.
my. 172800 IN NS ns-my.nic.fr.
my. 172800 IN NS dns.mynic.net.my.
my. 172800 IN NS ns20.iij.ad.jp.
;; Received 441 bytes from 192.36.148.17#53(i.root-servers.net) in 182 ms
klse.com.my. 86400 IN NS ens1.klse.com.my.
klse.com.my. 86400 IN NS ens2.klse.com.my.
;; Received 103 bytes from 61.6.38.139#53(ns5.jaring.my) in 6 ms
www.klse.com.my. 28800 IN NS sens2.bursamalaysia.com.
www.klse.com.my. 28800 IN NS sens1.bursamalaysia.com.
;; Received 90 bytes from 121.123.146.80#53(ens2.klse.com.my) in 5 ms
www.klse.com.my. 20 IN A 121.123.146.114
;; Received 49 bytes from 211.25.178.1#53(sens1.bursamalaysia.com) in 7 ms
A dig +trace gives a successful resolution, but the query fails when I try
to lookup either sens1.bursamalaysia.com or sens2.bursamalaysia.com (the
query will ALWAYS hits ens2.bursamalaysia.com which is the broken server)
# /usr/local/bin/dig sens1.bursamalaysia.com +trace
; <<>> DiG 9.7.0 <<>> sens1.bursamalaysia.com +trace
;; global options: +cmd
. 491534 IN NS f.root-servers.net.
. 491534 IN NS c.root-servers.net.
. 491534 IN NS b.root-servers.net.
. 491534 IN NS j.root-servers.net.
. 491534 IN NS d.root-servers.net.
. 491534 IN NS a.root-servers.net.
. 491534 IN NS m.root-servers.net.
. 491534 IN NS g.root-servers.net.
. 491534 IN NS l.root-servers.net.
. 491534 IN NS h.root-servers.net.
. 491534 IN NS e.root-servers.net.
. 491534 IN NS i.root-servers.net.
. 491534 IN NS k.root-servers.net.
;; Received 492 bytes from 192.168.10.209#53(192.168.10.209) in 30 ms
com. 172800 IN NS d.gtld-servers.net.
com. 172800 IN NS a.gtld-servers.net.
com. 172800 IN NS c.gtld-servers.net.
com. 172800 IN NS b.gtld-servers.net.
com. 172800 IN NS m.gtld-servers.net.
com. 172800 IN NS f.gtld-servers.net.
com. 172800 IN NS g.gtld-servers.net.
com. 172800 IN NS l.gtld-servers.net.
com. 172800 IN NS h.gtld-servers.net.
com. 172800 IN NS e.gtld-servers.net.
com. 172800 IN NS i.gtld-servers.net.
com. 172800 IN NS k.gtld-servers.net.
com. 172800 IN NS j.gtld-servers.net.
;; Received 497 bytes from 192.33.4.12#53(c.root-servers.net) in 428 ms
bursamalaysia.com. 172800 IN NS ens1.bursamalaysia.com.
bursamalaysia.com. 172800 IN NS ens2.bursamalaysia.com.
;; Received 111 bytes from 192.41.162.30#53(l.gtld-servers.net) in 275 ms
;; Received 41 bytes from 121.123.146.80#53(ens2.bursamalaysia.com) in 5 ms
Does this make sense?
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