quicker DNS propagation

Yann Shukor
Yann Shukor used Ask the Experts™
on
Hi

One of my clients runs some of his servers in certain regions around the globe where Internet access is a little flaky.

Local servers at these remote sites cater for two types of users, internal staff and external partners. Both of these groups of users actually access the company application using the same URL. The DNS servers handle the pertinent redirections.

To overcome frequent disconnections, users can be redirected to a server located at a neighbouring site.

When this occurs though, the internal users are redirected towards the updated IP address pretty quickly, whereas the external users have to wait for 'Internet' DNS propagation to occur, and the time lag can be quite significant sometimes.

Is there a way to accelerate the propagation of DNS changes at all ?
Has anyone come up with alternative solutions to deal with the situation described above ?

thanks

yann
Comment
Watch Question

Do more with

Expert Office
EXPERT OFFICE® is a registered trademark of EXPERTS EXCHANGE®
Top Expert 2011

Commented:
"Internet propagation" or "Global DNS propagation" is a fallacy usually perpetrated by ISP's and hosting providers so that the customer doesn't expect immediate results to their DNS request.  All that matters here is the TTL of the records in question.  It sounds like you have split views for DNS (internal sees different zones than external), so change the TTL of your external records to something reasonably short like 300 (5 minutes).

All RFC compliant resolvers will have your new IP within 5 minutes.

Author

Commented:
thanks Papertrip,
will check this out

Author

Commented:
Apparently the client has already toyed around with the TTL setting
but this hasn't brought about any improvements
Fundamentals of JavaScript

Learn the fundamentals of the popular programming language JavaScript so that you can explore the realm of web development.

Commented:
For sites hosted on Apache, you can use ProxyPreserveHost and ProxyPass parameter in the virtual host.

ProxyPreserveHost On

ProxyPass / [FQDN of the new server]

This will forward requests coming to old IP to the new server.
Once the DNS has full propagated, these can be taken off.

Commented:
The problem even with a very short TTL (like 5 min), is that you cannot control how other DNS servers are caching it. They might refuse to use so short TTL, so they set it something like 30 min as a minimum (Googles DNS 8.8.8.8 for example don't really care if you set TTL too low).

Since the URL you are trying to reach in case of lost internet is in another location than the primary server, I think the best solution would simply be to add a second A/CNAME record for the second site and inform your users to use the second one in case the primary is failing. Of course if your application will work with a second record.
Commented:
Thanks san1074, I have forwarded your suggestion to my client.

Thanks also xcomiii because this in facts brings us back to the traditional approach of employing a backup solution, here being a backup URL.

Not sure if the client will favour this option since it can instill a certain amount of confusion for the users, and require the to need to revert to the original original URL once things return to normal.

This suggestion does bring to mind the role of dynamic DNS management as provided by the likes of DynDNS.org

Rather than have to suffer the unforseeable delays of DNS update propagation, why not employ a dynamically managed address. This would be quasi immediately updated whenever the server's email address would change, by the client utility located on the server.

This would solve the situation for the external partners; as for the local users, well the local DNS server would simply point the Dyndns.org URL in the right direction.

Does this seem feasible ?

thanks

yann

Author

Commented:
dns propagation isn't controllable

Do more with

Expert Office
Submit tech questions to Ask the Experts™ at any time to receive solutions, advice, and new ideas from leading industry professionals.

Start 7-Day Free Trial