REST message connection refused: target host unreachable

Network firewall rules are blocking outbound HTTP/HTTPS traffic from ServiceNow instance to the target host on the required ports. (high likelihood)

MID Server is offline, misconfigured, or not properly routing traffic when the REST message is configured to use a MID Server for connectivity. (high likelihood)

Target hostname or IP address is incorrect, misspelled, or the target service is down or moved to a different endpoint. (medium likelihood)

Proxy configuration issues preventing the ServiceNow instance from reaching external hosts through corporate proxy servers. (medium likelihood)

DNS resolution failure where the hostname cannot be resolved to an IP address from the ServiceNow instance or MID Server. (low likelihood)

Step 1: Navigate to System Web Services > Outbound > REST Message and locate the failing REST message to verify the endpoint URL is correct and accessible.

Step 2: Check System Diagnostics > Log > Application Log for detailed error messages and verify the exact timestamp and context of the connection failure.

Step 3: If using a MID Server, navigate to MID Server > Servers and confirm the MID Server status is Up and verify it can reach the target host from its network location.

Step 4: Test network connectivity by using the built-in REST Message test functionality or create a simple test script to isolate the connection issue from business logic.

Step 5: Review proxy settings under System Properties > Web Service and ensure outbound proxy configuration matches your network requirements if using a corporate proxy.

Step 6: Contact your network administrator to verify firewall rules allow outbound traffic on the required ports (typically 80/443) from your ServiceNow instance or MID Server IP addresses.

Step 7: Verify DNS resolution by checking if the hostname resolves correctly from the ServiceNow instance or MID Server using network diagnostic tools.

Step 8: If the target service requires specific network routing, configure the REST message to use an appropriate MID Server located in the correct network segment.