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In addition to host_vars and group_vars, Ansible supports the definition of variables using other techniques, including the following:

• Using the vars keyword within the play to specify multiple variables
• Using vars_files to define variables in a file and having Ansible read these variables from this file while running the playbook
• Specifying variables at the command line using the --e option

In addition to the user-defined variables that we can specify, Ansible has some default variables that it builds dynamically for its inventory. The following table captures some of the most frequently used variables:

inventory_hostname	The name of the hosts as defined in the inventory (for example, csr1 and mx1)
play_hosts	A list of all the hosts included in the play
group_names	A list of all the groups that a specific host is a part of (for example, for csr1 this will be [edge, Cisco, network])