[NCSA-discuss] DNS Questions

[Joseph Mack NA3T]

On Tue, 21 Feb 2006, Matt Pusateri wrote:

> One of the things you can do to help propagation speed up 
> is to set the time to live down on your existing name 
> servers so that people cache them for a shorter period of 
> time(you will have to have ait do this though).

AFAIK core nameservers ignore your TTL so that they don't 
have to update all their records every minute. If I was 
running a nameserver, I wouldn't accept short TTLs. When I 
tried it on my changeover a few days ahead, none of the 
machines accepted the short TTL (yes I updated the serial 
number).

You might have trouble getting some already uncooperative 
nameserver hoster to change your TTLs anyhow.

I haven't done a changeover in many years. It seems that 
changes are propagated a lot faster nowadays.

Here's an approach many people seem to use.

Your ISP is listed as the primary nameserver. You have your 
own machines at your site, which are listed as the 2ndary 
name servers. In reality the machine at the ISP is a caching 
secondary and just listens for updates from your machines. 
You never have to call up the ISP to enter updates. If you 
need to change ISPs later, first you add install another 
secondary nameserver at your new ISP. When you're ready, let 
whoever know that this machine is your new primary.

Of course this doesn't work if you have to change the IPs of 
all of your machines too.

Can you have duplicate machines/IPs available during the 
changeover providing identical services?

Joe

-- 
Joseph Mack NA3T EME(B,D), FM05lw North Carolina
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