Patton electronics CopperLink 2168 User Manual page 8

Ethernet Extenders automatically add and delete MAC addresses, only
passing packets across the CopperLink link that are meant for the remote
peered LAN.
Figure 1. Typical application
The CopperLink/L modem and CopperLink/R modem work together to
create a transparent extension between two peered Ethernet LANs.
Figure 1 shows a typical point-to-point application.
8