正解:A
The ETR, or Egress Tunnel Router, in LISP (Locator/ID Separation Protocol) is responsible for publishing EID-to-RLOC (Endpoint Identifiers to Routing Locators) mappings for a site. This is part of the LISP control plane, which separates the endpoint identity namespace (EID) from the routing locator namespace (RLOC), with the ETR functioning as the component that advertises these mappings to the rest of the network, allowing for proper routing and forwarding of packets to their intended destinations.