VSS fails with the error:
RPC error:The RPC server is unavailable. Code: 1722
In rarer cases dynamic port allocation needs to be configured.
Note: If the VM that is failing to be connected to is Windows Server 2003, you need to use the RPC Configuration Tool (RPCCfg.exe) from the Windows Server 2003 Resource Kit to complete the process that is described in this article.
Additional troubleshooting steps can be found in the following Microsoft KB article:
A full list of used ports can be found here: https://helpcenter.veeam.com/docs/backup/vsphere/used_ports.html#ms_servers
When Veeam Backup & Replication connects to a VM it creates firewall exclusions for the ports and processes it uses. Veeam Backup & Replication however is not able to add firewall exclusions to hardware or third-party software firewalls.
The most common ports that cause this issue when using Application-Aware Image Processing are the Dynamic RPC ports that the temporary guest agents are assigned.
These ports are:
Note: The NIC’s Network Location being set to Public mode will also cause this, as Public mode sets the firewall it’s strictest settings.
When no job is processing the VM connect to it and check the following things:
Please review the full list of Antivirus/Antimalware exclusions listed here: http://www.veeam.com/kb1999
The most common solution is to exclude the C:\Windows\VeeamVSSSupport\ folder from being scanned.
To configure dynamic port allocation follow the steps outlined in the following Microsoft KB article. These changes will need to be made on the server that Veeam Backup & Replication is having trouble connecting to.