In this Linux quick tip we will discuss using command line options to force the SSH client to use IPv4 or IPv6 specifically. We will also show you how to set which IP protocol you would like to use in your SSH client configuration file.
Command Line Options to Force SSH Client to Use IPv4
There are two, very easy to remember, command line options to force specific versions of the internet protocol. Simply adding a
-4 option on the command line will force the SSH client to use IPv4.
Here is an example:
ssh -4 [email protected]
Command Line Options to Force SSH Client to Use IPv6
You probably guessed it by now, but there is also a
-6 option that allows you to force the use of IPv6.
Here is an example:
ssh -6 [email protected]
Setting IPv4 or IPv6 in Configuration Files
In an earlier article titled “Configure Host Specific SSH Settings” we discuss building configuration files for different hosts. If you would like to force IPv4 on a host without adding the command line option every time, just create or edit your
~/.ssh/config file and add one of the following lines under your host.
Set IPv4 Connection in SSH Client Configuration File
Here we use
inet to specify we want to use IPv4 for the SSH connection.
Set IPv6 Connection in SSH Configuration File
In this example, we use
inet6 to specify that we want to use IPv6 for the SSH connection.
Here is an example of an SSH client configuration file with a host using IPv6 on port 2222 and using SSH keys for authentication.
Host putorius.net IdentityFile ~/.ssh/id_putorius_rsa IdentitiesOnly yes ForwardX11 yes Port 2222 AddressFamily inet6
It’s simple to force IPv4 or IPv6 for your SSH connections. It is one of those times when the command line option seems so simple, but hard to guess.
If you are anything like me you are now wondering why inet? Inet simply stands for Internet Protocol family. It is widely used in Linux network connections of many services. You can read more about inet in the links below.
Links and Resources
Force SSH Client to Use IPv4 or IPv6
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