3679263 - HTTP 502 Bad Gateway raised from CPI

While working with CPI, following error is raised:

====
Could not send message, HTTP response 502: Bad Gateway. Unable to open connection to backend system when communicating with https://<target host>:<port>/<URI>
====

From SCC trace (ljs_trace.log / scc-core.trc), following is perceived:

====
20xx-xx-xx xx:xx:xx,0xx +0000#DEBUG#com.sap.core.connectivity.protocol.http.HttpOutboundConnectionProcessorFactory#tunnel-client-21-8#0x9080deea#Creating outbound protocol processor for protocol HTTP
20xx-xx-xx xx:xx:xx,0xx +0000#DEBUG#com.sap.core.connectivity.spi.processing.AbstractProtocolProcessor#tunnel-client-21-8#0x9080deea#Opening connection to backend system <hostame-of-backend-system>:443
20xx-xx-xx xx:xx:xx,0xx +0000#ERROR#com.sap.core.connectivity.spi.processing.AbstractProtocolProcessor#tunnel-client-21-8#0x9080deea#Unable to open connection to backend system: <hostame-of-backend-system>
java.net.UnknownHostException: <hostame-of-backend-system>
    at java.net.InetAddress.getAllByName0(InetAddress.java:1347)
====

• SAP Cloud Connector(SCC) release independent;
• DNS.

DNS, SCC, sap cloud connector, cloud connector, connector, UnknownHostException, domain name server, name resolution, resolve, resoling, /etc/hosts, hosts, backend system, http 502, 502, bad gateway,  , KBA , BC-MID-SCC , SAP Cloud Connector On-Demand/On-Premise Connectivity , Problem