Frame Relay “mapping” creates a correlation between a Layer 3 address and its corresponding Layer 2 address.  The concept is similar to the ARP cache for LAN interfaces.  Routers that use Frame Relay need a mapping between a router’s Layer 3 address and the DLCI used to reach that other router.

Definition of Mapping:

The information that correlates to the next-hop router’s Layer 3 address, and the Layer 2 address used to reach it, is called mapping.  Mapping is needed on multiaccess networks.

LMI status messages tell routers about VCs, the associated DLCIs, and the status.