Additional WAN Accelerator ports not listed in documentation may need configured.
This issue stems from not having the correct ports open for the use of the WAN Accelerator.
When configuring firewall, IDS, or antivirus, the following ports may need to be opened on source and target servers for the use of the WAN Accelerator in addition to TCP 6165:
b.) TCP 6164
In conjunction with standard server to proxy transmission ports specified by documentation: http://www.veeam.com/vmware-backup/help-center/vsphere/used_ports.html?zoom_highlightsub=ports