[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]

Re: [FC3] Sites 'disappearing' from DNS



On Mon, 2005-04-04 at 12:22 +0100, Andy Green wrote:

> Your ISP DNS is likely going slow every now and again -- watch it with
> tcpdump and see what you see.
> 
> Whatever machine at your site talks to the ISP DNS server is often
> giving up on the query before the response is received.  Then I guess it
> gives up and figures it's an NXDOMAIN.  There's a thing called negative
> TTL for DNS, basically if it got a response of NXDOMAIN once, it will
> for a fixed time not bother to check again but immediately say NXDOMAIN
> to queries.  I guess this is where your "it doesn't exist no matter what
> I do" period is coming from.
> 
> Then after the negative TTL is exhausted, it will check again with your
> ISP DNS, and depending on if your ISP DNS is fast enough or not, you
> either get through or have another period of negative TTL timeout.
> 
> Here's a suggestion: on the machine that talks to your ISP DNS, edit
> resolv.conf to add
> 
> nameserver xxx.xxx.xxx.xxx
> options timeout:25
> 
> This will get your machine to wait up to 25 seconds for a response from
> the ISP DNS server and should hopefully make the problem go away, if I
> understood it right.

    Well, I'll keep this idea in mind; but usually when Firefox is
problematic, the "can't get there" box comes up in about 1s...not as
much/over 25s.  But I appreciate the effort...

-- 
Those who entrust life and limb to Microsoft deserve neither. -Me, 2005
------------------------------------------------------------------------
Brian Fahrländer                 Christian, Conservative, and Technomad
Evansville, IN                                http://www.fahrlander.net 
ICQ: 5119262                                          AIM: WheelDweller
------------------------------------------------------------------------



[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]