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CrashPlan does it's best to try and connect to other computers without much configuration on your part, but sometimes you might need to adjust your firewall settings, especially after a CrashPlan upgrade or an operating system update.

Read more here.

The backups go directly to your own computers but they need our service to find each other and establish the connection. This is not user configurable. A connection can persist if one or both computers cannot connect to CrashPlan's servers, but this is not guaranteed. For example, if one computer's IP address changes while its Internet connection is down (and therefore can't connect to CrashPlan), the other computer may not be able to find it.

If you don't want to rely on our servers for the connection, you can use CrashPlan PRO, our business version.

“Destination unavailable. Backup location is not accessible” means that the location of the archive on the destination computer is not valid. This could be because the drive is not currently mounted or because permissions do not allow access.

Please see our troubleshooting guide in the How To section for more information.

CrashPlan tries to open random ports for listening as part of the rendezvous connection process. At this time there is no way to stop that. It won't happen if CrashPlan is able to connect to the other CrashPlan computer directly on TCP 4242 (by port forwarding, etc.). We recommend allowing all CrashPlan connections in your firewall.

In lay terms, if the destination computer is across the Internet, it is considered a WAN connection and the WAN bandwidth limits apply.

The technical definition is this:

If the computer you're trying to connect to has a routable IP address, then it is considered a WAN connection. If the computer you're connecting to does not have a routable IP address, it is considered a LAN connection and LAN bandwidth throttling settings are applied. Setting the bandwidth to None means no throttling.

The speed you see is the “effective speed” and not the raw speed. The effective speed takes into consideration data de-duplication, compression and incremental backup. So if you are sending (or receiving) a lot of duplicate data that compresses really well (e.g. lots of revisions of Word documents where “save as” was used frequently), it's possible to see very high numbers for speed.

• TCP 4242: listening port for computer to computer connections, can be configured under Settings > Backup > Inbound backup from other computers (required for computer to computer backup)
• TCP 4243: used by the CrashPlan application to connect to the CrashPlan backup service (required)
• TCP 443: for connecting the CrashPlan backup service to CrashPlan Central (required)
• TCP > 50000: NAT traversal for connecting between computers (optional)
• Standard UPnP and NAT-PMP ports: for connecting between computers (optional)

CrashPlan works extremely well and remains quite usable on high latency networks. There are many reasons for this, but mainly because:

• CrashPlan assumes the worst - It makes no assumptions about quality of link and is quite patient.
• CrashPlan is extremely efficient - Our binary protocol rides on top of TCP and doesn't waste a bit.
• CrashPlan is a streaming protocol - It does not rely on acknowledgements (ACK) from server when sending data. Data is streamed as fast as possible. The only ACK is a TCP ack in the underlying protocol.
• CrashPlan recovers - Backing up a large file? CrashPlan resumes within the file. So even a 1TB file can be backed up over poor line that keeps dropping.

We've been used on cellular networks (1G, 2G, 3G), satellites, DSL, Cable, Wireless and wired ethernet – all with great success.

Things you may notice in a high latency situation:

• Long delay when changing desktop preferences.
• Frequent restarts of backup due to disconnects.

It won't give up in these situations, it just keeps trying.