What is a Private IP?

I am about to create a new Linode, and one of the options is "Private IP". What is a "Private IP"?

A private IP is an unroutable IP address that allows you to communicate with other Linodes you may have located in the same datacenter.

And what are the benefits of it, opposed to not selecting it?

The key word here is "unroutable"…traffic on the datacenter private network is like traffic among computers on your home network, it doesn't spill out into the public internet.

Note that "private" is not the same as "secure". Communication among Linodes using the datacenter network is not secure unless you make it so.

I would only check the box if you need it. If you don't check the box and find you need/want it later, you can always add it.

-- sw

Let me ask this. If you create a brand new second Linode and wanted to transfer tons of files from the previous Linode (via scp or rsync), wouldn't a private IP help by cutting down on public network bandwidth?

When you create the private IP when creating the new Linode, will the first Linode automatically have access to it or do you have to do something to the first server?

Q1. Possibly. It would depend on the available bandwidth of the private network. Undoubtedly, Linode is not the data center operator’s only customer so it would be hard to make predictions about this.

Q2. Since the there probably isn’t a DNS server for the two nodes in this private network, you would have to use /etc/hosts to name them. The two IP addresses would be known to each however (using ARP). This can be easily verified with ping/ping6.

The setup here would be exactly the same as the LAN side of your home router.

— sw