CrashPlan does its best to connect to other computers without configuration on your part, but sometimes you do need to adjust your firewall settings, especially after a CrashPlan upgrade or an operating system update. Follow this step-by-step guide to get your computers connected.
In rare cases after an update, some users who made no firewall modifications could experience difficulty connecting to other computers. Following an update, a software firewall might identify the new release as a new application. Adjusting the software firewall or enabling port forwarding usually resolves the issue, even if you've never had to do this before.
Note: If you are using CrashPlan PROe, please see the CrashPlan PROe considerations below.
If you are attempting to set up two or more computers to back up to each other (known as computer-to-computer backup), the router and firewall settings may need to be properly configured for each computer involved in a computer-to-computer relationship.
IMPORTANT NOTE: The message "Unable to connect to the backup engine" is very rarely a network error. If you see this message, verify that no other applications are using the same ports CrashPlan needs to function. If that does not appear to be an issue, see our Unable to Connect to the Backup Engine article for further troubleshooting.
Multiple devices registered to the same user can be enabled to act as backup destinations for each other. CrashPlan PROe's NAT traversal feature is effective at allowing computer-to-computer backup between clients running on separate LANs.
You can attempt to re-authenticate with CrashPlan Central if you cannot connect.
Create the following firewall rules in any software or hardware firewall between the relevant computers:
See External Resources for links to manufacturer documentation about software firewalls built into the Mac or Windows operating systems.
If the CrashPlan app is unable to connect to the other computer after configuring the firewalls and routers, you should use telnet to troubleshoot the connection. If telnet cannot connect to the other computer, then something is blocking the connection, such as:
If the telnet connection fails, enable port forwarding on your router for incoming connections on TCP port 4242.
Enabling port forwarding is configured differently for each router manufacturer. You can review your manufacturer's documentation for details, or you can look for a guide at PortForward.com or HowToGeek.
If the telnet connection succeeds and you still can't connect with CrashPlan, proceed to step 5.
In some cases, after you configure port forwarding, you may need to restart the CrashPlan service on the source or the destination to get the network change to take effect.
If you have multiple computers running CrashPlan on a single network and you've tried everything up to this point, you may need to assign a unique listener port to each computer and configure port forwarding for each port. A symptom might be that one computer connects properly, but one does not.
Good port choices are between 1024 and 5999. Ports 1023 and below are special and should not be used. Before you set a new port, you can use the netstat command to see if any other programs are using the port you've chosen.
Choose another port if something is already listed under the number you've selected.
Once you find an unused port, you can change the listening port option in the CrashPlan app from Settings > General > Inbound backup from other computers>Listen port. Make sure to set up port forwarding for that port as well.