I have WAN1 and WAN2 connected ('always on' with 'load balance' ticked) to provide backup in the event of one line failing. Both have fixed IPs.

I run a mail server and an FTP server. The mail server is taken care of by defining two MX records so whichever line is active, incoming mail is OK.

However, for FTP I have to publish a fixed sub-domain (ftp.mydomain.co.uk) which can only point to one or other of the two lines.

I am trying to find the best way to maintain the ftp domain so that it points to whichever is the active line.

Using a DDNS service seems to be the way to go, so I have first tried this using a DDNS updater program. In principle it works but the IP of the domain keeps changing due to the load balance feature.

So I am trying to use the DDNS setup in the router, first to eliminate the need for an updater program but also in the hope that it will maintain a steady IP and only do an update if WAN1 has failed.

As per normal, the manual is not a lot of use, as well as being out of date.

I would like to know whether I can achieve what I want by specifying 'WAN1 first'? As long as WAN1 is up then its IP will be used to update the DDNS service thereby keeping the IP steady?

Also there is an undocumented option 'Determine Real WAN IP'. What does this do?

(I have seen the FAQ but that does not really explain anything even though it says last modified June 14 )

PS: Has anyone had any experience of using changeip.com for domain DNS hosting? I am looking for a reasonably priced service and saw the name in the Service provider dropdown list. At $9/year the price seems very reasonable. Are they any good?

I believe you are correct in your understanding of the 'WAN1 first' option.

However, this would be a cleaner option:

http://en.wikipedia.org/wiki/Round-robin_DNS

Now that you mention it I do remember reading about it some years back and went so far as defining two A records (I think that is all it needs) but concluded that it was not an ideal solution - though I no longer remember why.......

Just an update:

I have the router updating a domain I have at changeip.com and it is working.

However it is not doing it intelligently. I have it set to update every minute (important for me as a VoIP based switchboard is dependent of having the correct external IP) and the log at changeip.com shows it updating every minute, rather than only when there is a change of IP.

LesD wrote: However it is not doing it intelligently. I have it set to update every minute (important for me as a VoIP based switchboard is dependent of having the correct external IP) and the log at changeip.com shows it updating every minute, rather than only when there is a change of IP.

It's doing exactly what you asked it to; it's updating every minute. It will also update when there's a change of IP. Turn down the frequency of the auto-updates if you have a problem with it updating every minute.

Thank you - now I understand. And I now also understand why the default update interval is 14400 (10 days).

I should have realised that: "Auto-Update interval: Set the time for the router to perform auto update for DDNS service." does not mean what it says (actually it says nothing more than what the words 'Auto-update interval' say) but rather: "The router will auto-update whenever the IP changes, but if you want to force an update every once in a while then enter a figure here."

Thanks again.