Hint: Hosts are not scanned / not shown as "Alive"

Scanning / scan configuration
1

Some common issues if scans doesn’t return any results:

Note: If you have any questions on this topic please start a new thread for each question and link back to this topic so that it can be updated accordingly.

For all installations (Greenbone Community Edition/Greenbone Enterprise Appliances/VM and Source/Package like e.g. Kali Linux)

  1. The targets are not answering to an ICMP Echo Request → Check the Alive Test setting of your Target definition and try some of the other available methods. Further reading:

    10 Scanning a System — Greenbone Enterprise Appliance 22.04.6 documentation
    10 Scanning a System — Greenbone Enterprise Appliance 22.04.6 documentation

  2. You’re using a custom scan configuration which doesn’t include the following two VTs from the Port scanners family.

    Nmap (NASL wrapper) - OID: 1.3.6.1.4.1.25623.1.0.14259
    Ping Host - OID: 1.3.6.1.4.1.25623.1.0.100315

    Further reading:

    https://community.greenbone.net/t/hint-self-created-scan-configs-copy-of-empty-scan-config-showing-no-results/331

  3. You’re using a Port List which isn’t optimal for your environment:

    e.g. a All TCP and All UDP port list might be responsible for your portscan to time out causing your scan to not return any results at all. It is suggested to start with a smaller port list like e.g. All IANA TCP.

Only for own Source/Package installations (e.g. Kali Linux or Debian)

  1. SELinux is enabled and blocking the scanner from doing its job.
  2. You don’t have nmap installed or not available within your PATH

Further debugging / logging

The mentioned Nmap (NASL wrapper) and Ping Host VTs allows to configure various settings:

Ping Host

  1. Report about unrechable Hosts configured to yes: include notes if a remote host is considered as dead / not reachable and the reason why.

  2. Log failed nmap calls and Log nmap output configured to yes: Log additional output if nmap was used.

Nmap (NASL wrapper)

  1. Log nmap output configured to yes: Log additional output if nmap was used.
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