Fail-over

[Nicola Canepa]

I am writing a little patch for BIND which would allow failover between
a DNS server and another: you do a query, and if I cannot find a record
for a zone I am authoritative, I look in another zone/domain.

Could this be useful?

Nicola

On Tue, 2005-02-22 at 21:35 -0500, Kevin Darcy wrote:
> Norman Zhang wrote:
> 
> >>>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?
> >>>      
> >>>
> >>Probably the best way to do this would be to do BGP to both of the ISPs.
> >>With BGP, people will be able to get to your servers (with ISP1 IP
> >>addresses) through ISP2 when ISP1 is down.
> >>    
> >>
> >
> >Thanks for your suggestion. I can't use BGP. ISP1 and ISP2 are 
> >competitors. 8( Is there some way of doing this with BIND?
> >
> No good way, no. You could have a script automatically change the A 
> record (Dynamic Update would probably be the cleanest way) if it senses 
> a failure on the ISP1 connection. Unfortunately, you'd have to lower 
> your TTLs to low levels -- perhaps anti-socially low levels -- in order 
> to provide any kind of reasonable failover time for Internet clients.
> 
> The long-term solution is for browsers to use SRV records (think a level 
> of indirection above A records, with preferences and weighting, or, if 
> you prefer, MX records on steroids that aren't limited to mail 
> exchange). But adoption of the SRV mechanism seems to be taking a long time.
> 
>                                                                          
>                                           - Kevin
> 
> 
> 
-- 
Nicola Canepa <nicola.canepa at sys-net.it>
Veritas Certified Professional
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