Troubleshooting scan failures for hosts in DMZ

When you observe failures while scanning for hosts in DMZ, use the troubleshooting steps described in this section to either resolve the problem or create a BMC Support case.

Issue symptoms

• Scanning of hosts in DMZ fails with an error message, NoResponse(Unable to get the deviceInfo: NoSuchDevice).
• Though the scanning for hosts fails, a credential test succeeds, and it is possible to perform an SSH from the appliance CLI to the server.
• Nmap returns the message, Host seems down. If it is really up, but blocking our ping probes, try -Pn.
• In some cases, Nmap shows that the host is up with the message, Host does not respond to ping.

Issue scope

This issue can affect all versions of BMC Discovery.

Resolution

Try any of the following workarounds:

• In the Administration > Discovery Configuration UI, set the Ping hosts before scanning value to No.

  Important

  Use discretion when setting the Ping hosts before scanning field to No as it is a global setting and could have an adverse impact on your scan performance.

• In the Administration > Discovery Configuration UI, configure the Exclude ranges from ping field with the specific IP addresses or range of IP addresses that you want to exclude from a ping. These IP addresses will be pinged before scanning, by using nmap -Pn.
• When performing a discovery run, select the Do not ping before scanning option.

If the suggested workarounds do not work, create a BMC Support case and send the following details:

• Screenshot of the result generated after you perform a Test Credential for the target IP address.

• Run the following commands from the BMC Discovery command-line, and attach the output in the BMC Support case:

  /usr/bin/nmap --privileged -sT -sU -p T:21,22,23,80,135,443,513,902,4103,25030,25031,25032,5988,5989,6988,6989,U:161   <target ip address>
  
  /usr/bin/nmap --privileged -Pn  -sT -sU -p T:21,22,23,80,135,443,513,902,4103,25030,25031,25032,5988,5989,6988,6989,U:161    <target ip address>

• Go to the Administration > Discovery Configuration UI, take a screenshot of the Scanning section, and attach it to the BMC Support case. The screenshot must include the settings for the following fields:
  • Ping before scanning
  • Exclude ranges from ping