Introduction
When using Veeam to backup or replicate virtual machines over the internet to a service provider, most likely the service provider will be using Veeam Cloud Connect. By default, Veeam Cloud Connect uses port 6180 to receive incoming traffic from tenant (customer) locations.
If the service provider already has something listening on port 6180, they may want to try and use a different port other than 6180 for their Veeam Cloud Connect service. This should work with most Veeam applications and services; however, this usually will not work with CDP.
The Issue
Through may tests and working with Veeam support, it has been determined that CDP must use 6180 when transferring data. If port 6180 is changed on the service provider side for the Cloud Connect interface, CDP will make the connection from the tenant to the service provider and it will appear to be working; however, no data will ever transfer, it will just sit and appear to be stuck at the transfer data phase.
Veeam support has not confirmed why this behavior exists, but they have concluded that some part of CDP uses port 6180 to transfer data and this cannot be changed.
No Workaround or Solution
Unfortunately, when testing possible workarounds or looking for solutions for this, nothing seemed to work.
Attempts were made at the firewall to redirect the port using port translations. Software tools were installed directly on the service provider and tenant host systems to do port redirection before it ever leaves the server, allowing Veeam to use port 6180 then changing the port on the host, then changing the port back on the receiving host, back to 6180, attempting to trick Veeam into believing it truly is using port 6180. These failed as well.
Conclusion
Currently, Veeam is not aware of a fix or workaround at this time that will allow CDP to transfer data on a port other than 6180. This may be addressed in a future build or release, but there is no mention of that at the time of this writing.