Re: DNS cache

[Martin <marty () supine com>]

$author = "Dave Piscitello" ;
> I hope this is not too far off topic, but can anyone tell me what the 
> current "best practice" is for how frequently one should flush a DNS cache, 
> and if large enterprise practice differs much from:
>
> - local/regional ISP
> - mid-tier ISP
> - top-tier ISP

ummm... i might be mistaken but for all situations the only time you should
need to manually flush a cache is when you are made are aware that you have
been a victim of a cache poisoning attack...

if your DNS server follows the RFCs then it should be aging the cached
records and renewing the cache by querying for the record again when a 
client requests the same record (and dropping the record from the cache if 
no clients request it). the start of authority (SOA) part of a zone file
stipulates a default ttl and each rr can specify a ttl which sets how long
before your server expires the record from it's cache. some servers allow
you to set a maximum ttl which will override overly long ones...

read about ttl here http://www.jhsoft.com/help/df_ttl.htm

cheers
marty

--
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And true love wins
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