I have a Vigor 2950 load balancer connected through 2 Vigor 120 modems. If an FTP upload is interrupted either due to the remote site, local client or loss of connection on either of the ISP's connected through the 120's. I'm unable to resume the transfer as I was before the 2950 was installed and just a single connection to an ISP was being used. I'm assuming that on trying to resume the upload the 2950 might have chosen to make the transfer via the other broadband connection and therefore the recipient see it as a completely different connection.
Is there any way of forcing all FTP up through a singular WAN connection (IP Address). Meaning that any communication between host and client is with the same IP Address.
Cheers

I have a similar issue. 2 ADSL lines, one on DSL port the other on WAN2. I can't connect via passive FTP (for various reasons), but active FTP connects OK (but has separate issues for my setup).

I'm not 100% sure on your setup, but using active FTP should mean that the Vigor router will then modify the internal\external IP in use, thereby allowing traffic to go via either line without causing any subsequent resume issues.

They both have their pros and cons from a security point of view. I have NAT in the equation as well so still trying to find an acceptable solution!