[wplug] OT - request for comment on an idea

[Poyner, Brandon]

The concept of primary and secondary in name servers only applies to
which server has the master copy of the zone record.  When a 3rd party
name server does a recursive lookup for your domain it is going to get a
list of NS records for your domain and choose a name server at "random"
(it's not entirely random but that's another matter).  You can't set a
priority or make one name server more authoritative than another.  

As for your question about caching records, the best you can do there is
set the time to live (TTL) as low as you can tolerate.  Set it too low
and could have many DNS requests to deal with, and possibly more failed
or slower DNS lookups.  Another factor is that some name servers will
completely ignore your specified TTL and cache answers for much longer
(sometimes days), there is nothing you can do about that.  They're
typically far and few between however.

Brandon Poyner
Network Engineer III
CCAC - College Office
412-237-3086
 
 

> -----Original Message-----
> From: wplug-bounces+bpoyner=ccac.edu at wplug.org 
> [mailto:wplug-bounces+bpoyner=ccac.edu at wplug.org] On Behalf 
> Of Chris Romano
> Sent: Friday, June 03, 2005 1:58 PM
> To: General user list
> Subject: [wplug] OT - request for comment on an idea
> 
> I guess this is OT because it doesn't direct discuss F/OSS but it will
> involve F/OSS apps.
> 
> I am trying to create a BC/DR plan and I have an idea about a failover
> web/email server for my company but would like some comments on it
> from the group.  There is more insight and experience on this list
> that I could get through reading stuff from google and what not.
> 
> Currently we house our web/email/db servers here in-house and verizon
> does our DNS.
> 
> I would like to manage our DNS internally and not have verizon host
> it.  I would setup two DNS servers; one server will be here (primary)
> and the second one will be at an off-site datacenter (secondary).
> 
> On the secondary server I want to have a copy of our website/db/email
> systems.  The services will not be running by default but will have
> up-to-date data.  The reason for this is, I want a heartbeat between
> the primary and secondary servers.  If secondary DNS detects the
> heartbeat is down, it will start the web/db/email daemons and load new
> zone files that point to itself for our website and email.  This way
> if our circut goes down, our site will still be accessable.
> 
> Now from my understanding if a DNS server can contact the primary DNS
> of the site/name that it is looking for, it will try the secondary DNS
> for that site/name.  Is this right?  If so, this means that there
> shouldn't be to much downtime if this where to happen.  I problem is
> if the IP is cached on the requesting DNS server.  I am not too
> familiar with DNS yet, so in this case will the site be down until the
> requesting DNS server refreshes it's cache?
> 
> So is there a better way of doing this or am I at least somewhat on
> the right track?  I hope that I explained that well enough.
> 
> Thanks,
> Chris
> 
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