The following items are components to configure basic router parameters.
interface
A logical IP routing interface. When created, attributes like an IP address, port, link aggregation group or the system can be associated with the IP interface.
address
The address associates the device system name with the IP system address. An IP address must be assigned to each IP interface.
system interface
This creates an association between the logical IP interface and the system (loop-back) address. The system interface address is the circuit-less address (loop-back) and is used by default as the router ID for protocols such as OSPF and BGP (if supported by the platform).