Choosing authoritative nameservers
Matus UHLAR - fantomas
uhlar at fantomas.sk
Wed Jun 2 12:39:56 UTC 2010
On 02.06.10 16:20, Elias wrote:
> 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?
there's algorithm preferring the server with fastest responses but
ocasionally tryiong other servers.
> 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.
it's most probably not caused by server selection in BIND but in broken
delegation.
this is provided by com.my. sevrers:
> 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
ens1.klse.com.my. 86400 IN A 211.25.178.3
ens2.klse.com.my. 86400 IN A 121.123.146.80
This is provided by delegated servers:
;; ANSWER SECTION:
klse.com.my. 28800 IN NS ens1.bursamalaysia.com.
klse.com.my. 28800 IN NS ens2.bursamalaysia.com.
;; SERVER: 211.25.178.3#53(211.25.178.3)
klse.com.my. 28800 IN NS ens1.bursamalaysia.com.
klse.com.my. 28800 IN NS ens2.bursamalaysia.com.
;; SERVER: 121.123.146.80#53(121.123.146.80)
- we can safely say STOP here, the delegation is broken, fix it.
However, looking at bursamalaysia.com domain... Delegation:
;; AUTHORITY SECTION:
bursamalaysia.com. 172800 IN NS ens1.bursamalaysia.com.
bursamalaysia.com. 172800 IN NS ens2.bursamalaysia.com.
;; ADDITIONAL SECTION:
ens1.bursamalaysia.com. 172800 IN A 211.25.178.3
ens2.bursamalaysia.com. 172800 IN A 121.123.146.80
while ens1.bursamalaysia.com. returns same list of namservers, but does not
return glue records for them, the ens2.bursamalaysia.com. returns SERVFAIL
for bursamalaysia.com.
It's even more broken.
--
Matus UHLAR - fantomas, uhlar at fantomas.sk ; http://www.fantomas.sk/
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