Koozali.org formerly Contribs.org

Internal versus External DNS for mobile devices

Internal versus External DNS for mobile devices
« on: November 23, 2012, 04:31:06 AM »
For access to IMAP email I have setup my SME server to that on the internal network the name mail.mydomain resolves to the internal IP address of the server. Then outside my local network I have setup my DNS so that mail.mydomain resolves to the external IP address of my server.

In that way I can have a single setting in the email clients of mobile devices and it automatically connects to the server regardless of being inside the local LAN or outside.

However, I am finding that on my (android) phone, it very often has trouble contacting the server after I have left the office. I noticed the problem disappears when the phone got rebooted and I never notice the problem when coming into the office.

I am starting to think this issue my be to do with the DNS Time-To-Live.

My outside DNS is setup with a relatively short TTL of a few minutes so coming into the office is never a problem. When moving from inside (WiFi) to outside the office (3G) the problem resolves when rebooting the phone (i.e. DNS cache cleared?).

Does this sound like a fair assessment of what the problem could be?

Im not that familiar with tinydns but it looks like I would need to add a TTL value at the end of the line of the relevant records in /var/service/tinydns/root/data

Like in:

Code: [Select]
+mail.through-ip.com:10.1.0.21:120
Does this look correct?

Any feedback would be appreciated.

Regards,

Marco


Adelaide - Australia