Choosing authoritative nameservers

[Matus UHLAR - fantomas]

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. 


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Matus UHLAR - fantomas, uhlar at fantomas.sk ; http://www.fantomas.sk/
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