IP failover/migration question.

Andy Davidson andy at nosignal.org
Tue Jun 27 13:51:30 UTC 2006



Hi, guys

Very late reply, but this is a 'hot topic' in my space..

On 12 Jun 2006, at 04:02, Randy Bush wrote:

>> I'm trying to get a more clear understanding as to what is  
>> involved in
>> terms of moving the IPs, and how fast it can potentially be done.
> can we presume that separate ip spaces and changing dns, i.e. maybe
> ten minutes at worst, is insufficiently fast?

Ten minutes at worst, only if everyone is behaving.  Some of the UK's  
largest (in terms of consumer customer numbers) ISPs disobey short  
dns refresh times, and will cache expired or old records for 24(+?)  
hours.

Popular web browsers running on popular desktop operating systems  
also display extra-long dns cache time 'bugs'.


24 hours + outage whilst stale dns disappears will never do in  
internet retail.  BGP, two datacentres, both equivalent endpoints for  
customer traffic, same IP space, and an e-commerce application which  
will happily run 'active/active' is the holy grail, I think.  The  
problem isn't setting this up in IP, it's getting your commerce  
application to fit this model (a problem I have today).


Best wishes,
Andy



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