DNS Negative Caching

[Harshith Mulky]

I have a confusion on how the clients respond to and cache when particularly we receive negative replies from a DNS Server, particularly NXDOMAIN or SERVFAIL responses

on the DNS Zone file we have these records
$ORIGIN e164.arpa.
@   IN     SOA  picardvm2.e164.arpa. e164-contacts.e164.arpa.  (
                                2002022404 ; serial
                                3H ; refresh
                                15 ; retry
                                1w ; expire
                                3h ; minimum
                               )

so 3h is basically the amount of time clients are asked to cache negative results.

Now on the client side at lwresd.conf, if I have 

max-ncache-ttl 300

Will the client override the default 3h value sent as response from the DNS Sever for the zone e164.arpa


How are Negative responses usually cached?

Thanks
Harshith
 		 	   		  
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