The port-list is a list of monitor ports that transmit identical copies of mirrored packets. The loopback-port is an unused port that is required when you mirror to a port-list. The loopback-port is not available for switching user data traffic. Certain L2 control protocol packets, such as STP, LACP, and LLDP, cannot be mirrored with one-to-many mirroring. The remote IP address option allows you enable hardware mirroring of Ethernet frames to a specified remote IPv4 address, which can reside zero or more router hops away.
For high availability, you can add up to four redundant remote IP addresses. If you are adding another (redundant) remote IP address to an existing mirror that already has a remote IP address configured, you must use the add option.