Re: DNS Failover
A new DNS resolution is required if a single A record is returned. The only
version of IE that does a new DNS resolution without being restarted is
WinXP SP2. Microsoft was notified that GSLBs do not work correctly for
failover with single A records, some of the vendors worked with them, and
they changed the behavior in the release that came out a few weeks ago.
WinXP SP1 and previous versions of IE, and NetScape (i.e. the vast majority
of Internet clients) have the issue. I don't know about Firefox etc.
Browsers aside, many proxy servers will defeat what you are trying to do
with failover and your GSLBs.
----- Original Message -----
From: "Maria Iano" <firstname.lastname@example.org>
Sent: Thursday, October 14, 2004 7:53 AM
Subject: Re: DNS Failover
> We use GSLBs for load balancing between web sites but mostly for failover
> in case a primary site goes down. Usually they work pretty well. It's true
> that some name servers don't handle TTLs properly, but from my experience
> at watching the traffic I can tell you that it works for the vast
> Personally I haven't found it to be the case, as stated in the article you
> mention, that I have to restart my browser for the new A record to take
> effect. It has been my experience that the browser catches on and goes to
> the new IP pretty much immediately. The browsers I use most frequently are
> Firefox, Safari and IE. They are recent versions. Maybe the problems you
> describe occurred with older versions?...
>> -----Original Message-----
>> From: [email]email@example.com[/email] [mailto:firstname.lastname@example.org] On
>> Behalf Of Pete Tenereillo
>> Sent: Thursday, October 14, 2004 9:00 AM
>> To: Greg Maccarone; Anthony Wilkins
>> Cc: [email]email@example.com[/email]
>> Subject: Re: DNS Failover
>> Anthony mentioned he has a Web app, so that TTL trick won't work
>> The low TTL would be seen by servers "throughout the rest of the world"
>> TTL are ignored by most clients (and many proxy servers), so all
>> users (and users that share such proxies) will be stuck on the downed
>> server. Check out:
>> for details. IMO for failover you are better off putting both servers at
>> same site, using local load balancing (there are some very cost
>> solutions available now) and redundant power and Internet connections.
>> ----- Original Message -----
>> From: "Greg Maccarone" <firstname.lastname@example.org>
>> To: "Anthony Wilkins" <email@example.com>
>> Cc: <firstname.lastname@example.org>
>> Sent: Tuesday, October 12, 2004 11:46 AM
>> Subject: Re: DNS Failover
>> > On Tue, 12 Oct 2004 11:01:45 +0200, Anthony Wilkins
>> > <email@example.com> wrote:
>> >> Hi, is there anybody who can help me in finding a solution to a[/color]
>> >> I have?
>> >> My web server is sometime temporarily down and I want people to go to[/color]
>> >> remote site where I have a backup web server. Can I change DNS on the
>> >> Internet fast enough for incoming requests to be handled by my[/color]
>> >> web server? Normally I don't want traffic to go to the remote site.
>> >> Thanks, Anthony W.
>> > A way this could be achieved with DNS is to have a low TTL on the host
>> > entry that could be changing because of the outage. Then in most
>> > cases it would take no longer than the specified TTL for the changes
>> > to be seen throughout the rest of the world.
>> > my $.02.
>> > --
>> > Greg Maccarone
>> > [email]firstname.lastname@example.org[/email]