Fail-over

[Pete Tenereillo]

Whether this makes the situation better or worse depends on the situation 
itself. What Eddy was saying is that the browser's built in failover 
mechanism helps with ... well, failover.

Unfortunately, to use that mechanism you must configure your authoritative 
nameserver (or GSLB device) to return multiple A records, and that breaks 
what Norman initially stated he wanted to do (strict active/standby) ... so 
in that sense the use of the browser's failover mechanism does make the 
situation "worse" ... which is what Pete Ehlke was saying.



----- Original Message ----- 
From: "Pete Ehlke" <pde at rfc822.net>
To: <comp-protocols-dns-bind at isc.org>
Sent: Wednesday, February 23, 2005 1:04 PM
Subject: Re: Fail-over


> On Wed Feb 23, 2005 at 19:25:35 +0100, Eddy wrote:
>>Norman Zhang wrote:
>>> Hi,
>>>
>>> I've a dual WAN router, currently some of my servers are bound with
>>> static IPs to ISP1. I like them to remain available on ISP2 if ISP1 goes
>>> down. Do I need dynDNS service for this? Or I can type in 2 different
>>> IPs for 1 serivce.
>>>
>>> e.g.,
>>>
>>> 1.2.3.4 IN www.example.com #ISP1
>>> 2.3.4.5 IN www.example.com #ISP2.
>>>
>>> But internet may still resolve to 1.2.3.4 despite ISP1 being down. May I
>>> ask what the best way to go about this?
>>>
>>> Regards,
>>> Norman Zhang
>>>
>>>
>>If it is only for web access (like the example shown) you are lucky,
>>because modern browsers have the own built-in fail-over. Fail-over
>>during a session (https or statefull web application) might get you in
>>trouble, with this simple approach.
>>
> Thsi is completely 100% wrong. Internal browser caching of DNS
> information makes the situion *worse*, not better. See
> http://www.tenereillo.com/BrowserDNSCache.htm
>
> -Pete
>
>
>