master slave different site different resolution

Torinthiel torinthiel at data.pl
Thu Jul 14 10:37:23 UTC 2011


On 2011-07-14 11:53, Gabriele Gabriele wrote:
> Ok, may be I was not so clear to explain..
>
>
> for example I have in my Master work site the our webmail
> "webmail.mydomain.com" that when Master work site in UP the resolution
> is 1.1.1.1 but if the master go down in My slave work site, my slave dns
> resolv "webmail.mydomain.com" with 1.1.1.1 but that site is down..... So
> it should resolv it with my backup/slave resolution 2.2.2.2

So, you have both DNS and HTTP servers on both 1.1.1.1 and 2.2.2.2?
And you want HTTP traffic to go to 1.1.1.1, except where it fails, than 
it should switch to 2.2.2.2?

First, you do realize that you need to thing of some way to synchronize 
those web servers. Second, if those are synchronized, why don't just put 
both IP addresses and have some weak load balancing?

If you really want IP to change when server fails, this is bad:
a) takes time to propagate - after failure you still have to wait TTL 
seconds before everyone uses new server.
b) puts more burden on your DNS servers and on clients, as you have to 
put short TTLs on those names
c) you have to develop a way to test for primary's site failure. And 
take care of false-positives.
d) you can't have normal master-slave setup, which leads to zone 
maintenance problems.

Regards,
  Torinthiel


>
>  > Date: Thu, 14 Jul 2011 17:42:56 +0800
>  > Subject: Re: master slave different site different resolution
>  > From: shorttag at gmail.com
>  > To: d_gabriele at hotmail.it
>  > CC: bind-users at lists.isc.org
>  >
>  > 2011/7/14 Gabriele Gabriele <d_gabriele at hotmail.it>:
>  > > Dear lists,
>  > >
>  > > I have an issue to resolve about 2 dns server Master/Slave.
>  > >
>  > >
>  > > The Master is positioned in a site with public ip 1.1.1.1 and all
> the public
>  > > dns resolutions point to 1.1.1.1
>  > > the Slave is positioned in a site whit public ip 2.2.2.2 and
> obviously all
>  > > the public dns resolutions point to 1.1.1.1
>  > >
>  > >
>  > > the problem born when my Master site go down, because the Slave should
>  > > change the dns public resolution whit 2.2.2.2
>  > > is it possible use bind for this?
>  > >
>  >
>  >
>  > Sorry my bad understanding for your statement.
>  > But since you have two servers, two public IPs, why not just publish
>  > these two as authority or cache only servers?
>  >
>  > Regards.



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