![]() ![]() One method used traditionally by administrators to find online hosts is to perform a ping sweep of their networks. For example, 192.168.2.5 is reported as being named In the above example, you can see that there are four hosts that had their system names resolved. Nmap done: 256 IP addresses (0 hosts up) scanned in 0.69 secondsĪs you can see, the List Scan does not perform a scan of the remote system(s) as each port is listed as 'not scanned', but is used to perform a reverse DNS lookup against each host. NOTE: If you have multiple DNS servers configured on the system conducting an Nmap scan, Nmap will use each of the DNS servers at the same time to help increase response time. Resolved names will be included as part of the scan results. When a List Scan is performed, Nmap will attempt to perform a reverse DNS lookup to identify the FQDN of the host(s) to be scanned. This technique is referred to as a List Scan and is performed with the -sL option. For example, a security professional conducting a penetration test may use this option to first check his work before performing a scan. Listing Targets to be Scanned (List Scan)īefore conducting a host discovery scan or sweep, an Nmap user may wish to examine the hosts that would be queried by the scan itself prior to conducting the scan. For more information on Nmap as well as instructions on how to conduct a basic port scan with Nmap, please review the previous EE article Nmap: Performing a Basic Scan. This article discusses host discovery features that are available in Nmap 5.0 and higher. Discovering hosts can help system administrators ensure that they are monitoring all systems for availability while security administrators can ensure each system adheres to their company's security policy. While most administrators use a security tool such as Nmap to perform a port scan to list available services on a remote system, Nmap can also be used to conduct a wide variety of functions that security and network administrators can find very helpful in discovering available hosts on the networks that they are responsible for. ![]()
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