In one of my Veeam Backup jobs I had two Windows 2008 R2 VM’s with the Windows Firewall enabled. The backup job failed with the error: RPC error The RPC server is unavailable. Code 1722.
You can find the error in the job Statistics screen:
This error is the result of enabling Application-aware image processing (Microsoft VSS) and the Windows Firewall. RPC by default doesn’t like to work through a firewall. But Microsoft has a fix for this. KB article KB154596 explains how to change the RPC settings within the Windows Registry. You need to add the following settings:
Ports REG_MULTI_SZ
Specifies a set of IP port ranges consisting of either all the ports available from the Internet or all the ports not available from the Internet. Each string represents a single port or an inclusive set of ports. For example, a single port may be represented by 5984, and a set of ports may be represented by 5000-5100. If any entries are outside the range of 0 to 65535, or if any string cannot be interpreted, the RPC runtime treats the entire configuration as invalid.
PortsInternetAvailable REG_SZ Y or N (not case-sensitive)
If Y, the ports listed in the Ports key are all the Internet-available ports on that computer. If N, the ports listed in the Ports key are all those ports that are not Internet-available.
UseInternetPorts REG_SZ ) Y or N (not case-sensitive
Specifies the system default policy.
If Y, the processes using the default will be assigned ports from the set of Internet-available ports, as defined previously.
If N, the processes using the default will be assigned ports from the set of intranet-only ports.
Or you can copy the following *.REG file and execute this on the Windows 2008 R2 VM.
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Rpc\Internet]
“Ports”=hex(7):35,00,30,00,30,00,30,00,2d,00,35,00,31,00,30,00,30,00,00,00,00,\
00
“PortsInternetAvailable”=”Y”
“UseInternetPorts”=”Y”
The next step is to add a firewall rule:
After changing these settings you need to reboot the VM.
Now you are able to run the Veeam Backup job with the Firewall enabled on a Windows 2008 R2 VM.
| Source | Link |
| Micrsoft.com | KB154596 |
ICT-Freak.nl 
I have removed the Veeam Transport software and reinstalled it with out removing the server or deleting any backup or replication jobs. after the software was removed i restarted the server and installed it again and it worked.