he ingress tunnel router (ITR) is responsible for finding EID-to-RLOC mappings for all traffic destined for LISP-capable sites. When the ITR receives a packet destined for an EID, it first looks for the EID in its mapping cache. If it's not there, the ITR sends a map-request to the map resolver, which then forwards the request to the appropriate map server that holds the desired mappings. References := LISP Overview - Cisco