DNS cache in Ubuntu?

[PleegWat]

Ryan Chan wrote:
> Hello,
> 
> On Sat, Dec 5, 2009 at 1:48 AM, Tom H <tomh0665 at gmail.com> wrote:
>>>> Is your question related to bind or djbdns? Or is it related to browsers?
>>> Ubuntu network feature, e.g. ping is using old DNS cache.
>> Install nscd
>> aptitude install nscd
>>
>> To flush
>> invoke-rc.d nscd restart
>>
> 
> I have not installed nscd, so just wonder why caching happen.
> 

Note the caching may not be happening on your local machine. If you're 
using a NAT router it may contain a dns cache, and your ISP will also 
have (caching) DNS servers.


$ dig www.google.com

; <<>> DiG 9.6.1-P1 <<>> www.google.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 2662
;; flags: qr rd ra; QUERY: 1, ANSWER: 7, AUTHORITY: 4, ADDITIONAL: 4

<snip a lot of answer data>

;; Query time: 25 msec
;; SERVER: 192.168.1.254#53(192.168.1.254)
;; WHEN: Sun Dec  6 13:43:30 2009
;; MSG SIZE  rcvd: 284


The lines near the end tell that the query was answered by 
'192.168.1.254#53', which is the DNS function of my local NAT router.