[CentOS] cashing named server

[Johnny Hughes]

On Tue, 2005-05-17 at 07:28 -0700, Lee Parmeter wrote: 
> I started the named server on CentOS and it seems to
> resolve DNS request OK, but it does not seem to retain the
> info for very long. From what I can tell using "dig", a
> domain's ip address is retained for less than 12 hours. So
> in the morning, it takes 4+ seconds to resolve again the
> first time. Is there an adjustment somewhere for this or is
> the caching named support not enabled by default? 
> 
> Also, I thought it would be faster if I set named to use my
> ISP's named server as the first choice. Where do I set this
> up, in root.hints?
> 
> Anyone who knows more about "named" please feel free to
> comment!
> 
> Thanks!
> Lee
> 

The owner of the domain controls how long DNS entries are cached.  If
you do a dig, one of the things you get from an authorized DNS server
for that domain is the TTL (time-to-live).  That is how many seconds
your entry will remained cached in a non-authoritative DNS server.

for example:
-------------------------------------------------------------------
dig www.yahoo.com

; <<>> DiG 9.2.4 <<>> www.yahoo.com
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 2270
;; flags: qr rd ra; QUERY: 1, ANSWER: 9, AUTHORITY: 10, ADDITIONAL: 2

;; QUESTION SECTION:
;www.yahoo.com.                 IN      A

;; ANSWER SECTION:
www.yahoo.com.          300     IN      CNAME   www.yahoo.akadns.net.
www.yahoo.akadns.net.   60      IN      A       68.142.197.89
www.yahoo.akadns.net.   60      IN      A       68.142.197.90
www.yahoo.akadns.net.   60      IN      A       68.142.197.73
www.yahoo.akadns.net.   60      IN      A       68.142.197.75
www.yahoo.akadns.net.   60      IN      A       68.142.197.76
www.yahoo.akadns.net.   60      IN      A       68.142.197.80
www.yahoo.akadns.net.   60      IN      A       68.142.197.83
www.yahoo.akadns.net.   60      IN      A       68.142.197.88

;; AUTHORITY SECTION:
akadns.net.             127047  IN      NS      asia5.akadns.net.
akadns.net.             127047  IN      NS      asia9.akadns.net.
akadns.net.             127047  IN      NS      eur10.akadns.net.
akadns.net.             127047  IN      NS      za.akadns.org.
akadns.net.             127047  IN      NS      zh.akadns.org.
akadns.net.             127047  IN      NS      eur3.akadns.net.
akadns.net.             127047  IN      NS      use1.akadns.net.
akadns.net.             127047  IN      NS      use9.akadns.net.
akadns.net.             127047  IN      NS      usw6.akadns.net.
akadns.net.             127047  IN      NS      usw7.akadns.net.

;; ADDITIONAL SECTION:
za.akadns.org.          526     IN      A       208.185.132.176
zh.akadns.org.          526     IN      A       63.208.48.46

;; Query time: 164 msec
;; SERVER: 192.168.0.2#53(192.168.0.2)
;; WHEN: Tue May 17 09:35:27 2005
;; MSG SIZE  rcvd: 424
---------------------------------------------------------------

So that will remain in cache another 127047 seconds :)
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