Fail-over

Anthony Wilkins anthony_wlkns at yahoo.com
Thu Feb 24 09:47:42 UTC 2005


Pete Ehlke wrote:
> 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
> 
> 
Hi,

I've found a tool on www.simplefailover.com called Internet Explorer 
Timeout Tuner that handles this situation fairly easy. This tool can be 
used to adjust Internet Explorer DNS caching, Keep Alive, and Server 
Info timeout settings, which can be very helpfull when testing DNS round 
robin and failover setups. See 
http://www.simplefailover.com/outbox/dns-caching.pdf

Regards,
Anthony Wilkins



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