Subject: [DNSOP] DNS cache problem in stub resolver(DNS client)

From: "venkatesh.bs" <[email-masked]>
Date: Mon, 31 Aug 2009 15:49:50 +0530

Hi all,  
I have one query regarding DNS cache maintaince in dns  stub resolver(DNS client Not server side cache maintainence), 
Whether DNS Cache should be based on per server address  or based on 
FQDN only. 

>>1. Query1: Domain name: "google.com" DNS IP: DNS_SERVER_1 - 
>result will 
>>be stored in DNS Cache Meanwhile,DNS Server IP got changed.
>>2. Query2: Domain name: "google.com" DNS IP: DNS_SERVER_2 - Should we 
>>have to query to DNS Server 2? or Should we have to get it 
>from DNS Cache?

Thanks in advance.
venkatesh.B.S

---

From: [email-masked]
Date: Mon, 31 Aug 2009 11:39:10 +0000

On Mon, Aug 31, 2009 at 03:49:50PM +0530, venkatesh.bs wrote:
> Hi all,  
> I have one query regarding DNS cache maintaince in dns  stub resolver(DNS 
> client Not server side cache maintainence), Whether DNS Cache should be 
> based on per server address  or based on FQDN only. 
> 
> 

	a stub resolver, sort of by definition does not have a cache.

	in the presence of a cache, what do you hold on to?  if I 
	query for the A record(s) of google.com, what will i get back?

	one rr or multiple?

	if multiple, do i put all the answers in cache or only the first one?

	how long do things stay in cache?

	if google.com changes its IP addresses - how long are your cache
	entries valid?  why?

	once you have the answers to these questions, you will know when 
	you will go back and ask again what the address record(s) for 
	google.com are.

	you might also read "DNS and BIND" - or go to the helpful DNS web pages -
	or even try "Ask Mr. DNS" for answers to these fairly basic questions.

--bill