Re: [cobalt-users] Newbie Questions -- help!

[Jeff Lasman <jblists@xxxxxxxxxxxxx>]

At 05:23 PM 3/14/00 -0800, you wrote:

> How long do secondary DNS servers hold the info. i.e. say my primary DNS
> dies all of a sudden, but httpd is still running. if someone tries to find
> my site, can they?

Still haven't bought a copy of "DNS and Bind", have you <smile>?

Page 90:
"If the slave fails to contact the master server(s) for _expire_ seconds, 
the slave expires its data. Expiring the data means the slave stops giving 
out answers about the data because the data are too old to be useful. 
Essentially, this field says: at some point, the data are so old that 
having _no_ data is better than having stale data. Expire times on the 
order of a week are common--longer (up to a month) if you frequently have 
problems reaching your updating source."

So look for the "expire" field in your SOA record. It's the fourth field; 
on DNS that I set up, I use 604800 seconds, or one week.

> > And people who try to find your website get told your connection is
> > temporarily down.
>
> Well, they get a browser error, anyway. :-)

A browser error saying your site can't be reached is probably better than 
one that says your domain doesn't exist <smile>.

> > What's refresh?  And where do you set it?
> >
> > My guess is you mean TTL.  Which you can set on the RaQ3, but not on the
> > RaQ2 (not using the gui, anyway).

> So when's cobalt gonna release raq3 sw for the raq2?

I don't know <smile>.  You can always update it yourself if you don't mind 
breaking your warranty <smile>.  Since the new version isn't well 
documented yet, I'm not going to bother.

> Yeah, I mean TTL. Sorry. Refresh does something else, but I'm no sure what
> it is.

Also from "DNS and Bind", page 90:

"The refresh interval tells the slave how often to check that its data are 
up to date."

> bash-2.03$ nslookup -type=soa nobaloney.net
> nobaloney.net
>         refresh = 43200 (12H)
>         retry   = 7200 (2H)
>         expire  = 1209600 (2W)
>         minimum ttl = 43200 (12H)
>
> My friend has a dynamic IP and uses yi.org for dynamic DNS. They have his
> TTL set to 2 minutes. :-)

They're obviously quite Internet unfriendly.  It's a good thing his site 
isn't too popular.  Too much DNS traffic is a bad thing, and can get a lot 
of aggressive admins to block your site completely.  I NEVER go lower than 
one hour, and only for a day or two surrounding changes.  Personally I 
prefer 24 hours, but I use 12H on these for historical reasons.  After all, 
<nobaloney.net> only changes every few years or so.

Does he have to update it at <yi.org>, or does his system notify them to do 
it automatically whenever his IP changes?

> > And it really doesn't matter; so many
> > major nameservers have been patched to ignore it <frown>.
>
> What do they do instead?

Use their own TTL; often measured in days.  This has been extensively 
discussed on the Internet Access and other professional ISP lists.

Jeff
--
Jeff Lasman <jblists@xxxxxxxxxxxxx>