On Sun, Sep 24, 2006 at 04:35:42PM -0700, tbnarvaez@yahoo.com wrote:
> I`d appreciate very much any help with the following problem:
>
> I have one web server connect to the internet via Provider A. By the
> way, the ip address asigned to that server (IP A) belongs to Provider A
> as well as the DNS server I use.
> The problem is that link is very unstable and it is constantly out of
> service.
>
> Because of this situation I am adding a second internet link with
> Provider B who will also assign its own IP address to my web server (IP
> B).
>
> In order for this to work I am thinking about doing the following:
> a). I will assign to the web server both IP addresses in the same NIC.
>
> b) In Providers A's DNS server I will assign to the web server two IP
> addresses: the one assigned by Provider A and the second one from
> Provider B.
>
> My questions are:
> 1. Is this all I should do?
> 2. Will it be any off time because of the DNS broadcast of the new IP
> address (or even the old IP Address)?
> 3. If link A fails will it be possible for a client to access the web
> server via Provider B's link even if the DNS server belongs to Provider
> A?
>
> Thanks in advance for any comments or suggestions.



If you are trying to have high-availability failover with this setup,
this won't work. Here is what will happen:

50% of the clients querying for your server's IP address will get IP
address A. 50% will get IP address B. Unless you choose some other
distribution, then they get that.

Those who get IP address A will see it when the service is up and not
see it when the service is down. There is no provision for failover.

Those who get IP address B will see it when the service is up and not
see it when the service is down. There is no provision for failover.

It doesn't matter who owns the DNS server, as long as it's well-
configured and available. [Redundant failover IS built into the
assignment of multiple DNS servers.]

DNS doesn't broadcast. Changes may take time to propagate, but once
out there, there's no broadcast effect.

--
Joe Yao
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