Can you please confirm if you also experience this: when target server is unreachable, wrong target_host and target_ip values are logged in analytics:
apigee=# select target_response_code, response_status_code, target_host, target_ip from analytics."development.dev.fact_1111" WHERE apiproxy = 'example-test' order by client_received_start_timestamp desc limit 2;
target_response_code | response_status_code | target_host | target_ip
----------------------+----------------------+---------------------------------------------------+--------------------------------------------------------------
| 503 | (not set) | example.com/203.0.113.5
200 | 200 | example.com | 203.0.113.5
(2 rows)