nmap是一款非常强大的工具，可以扫描icmp,tcp,udp协议，支持端口扫描和主机存活扫描
一.安装
yum install nmap
二.命令
通过icmp方式，扫描出局域网中可以用的主机
# nmap -sP 192.168.1.1/24Starting Nmap 6.40 ( http://nmap.org ) at 2017-01-08 12:58 CSTNmap scan report for 192.168.1.1Host is up (0.0038s latency).MAC Address: 8C:F2:28:4B:02:FA (Unknown)Nmap scan report for 192.168.1.100Host is up (0.075s latency).MAC Address: 74:23:44:07:63:BB (Unknown)Nmap scan report for 192.168.1.101Host is up (0.00037s latency).MAC Address: FC:F8:AE:5D:56:47 (Intel Corporate)Nmap scan report for 192.168.1.102Host is up (0.075s latency).MAC Address: 1C:48:CE:17:A2:87 (Unknown)Nmap scan report for 192.168.1.105Host is up (0.073s latency).MAC Address: 00:F8:1C:C3:7D:AE (Unknown)Nmap scan report for 192.168.1.107Host is up (0.11s latency).MAC Address: F4:09:D8:54:92:AA (Unknown)Nmap scan report for 192.168.1.211Host is up (0.00073s latency).MAC Address: 00:0C:29:9A:41:ED (VMware)Nmap scan report for 192.168.1.110Host is up.Nmap done: 256 IP addresses (8 hosts up) scanned in 2.43 seconds
通过半开放模式或全开放模式扫描主机所有可以检测到的端口
注意：-p参数是端口范围，默认是1-1024
nmap -sS 192.168.1.101 -p 0-9000Starting Nmap 6.40 ( http://nmap.org ) at 2017-01-08 12:55 CSTNmap scan report for 192.168.1.101Host is up (0.0020s latency).Not shown: 8996 filtered portsPORT STATE SERVICE135/tcp open msrpc139/tcp open netbios-ssn445/tcp open microsoft-ds1540/tcp open rds3389/tcp open ms-wbt-serverMAC Address: FC:F8:AE:5D:56:47 (Intel Corporate)使用udp方式扫描udp端口
# nmap -sU 192.168.1.101 -p 0-9000Starting Nmap 6.40 ( http://nmap.org ) at 2017-01-08 13:02 CSTNmap scan report for 192.168.1.101Host is up (0.00080s latency).Not shown: 9000 open|filtered portsPORT STATE SERVICE137/udp open netbios-nsMAC Address: FC:F8:AE:5D:56:47 (Intel Corporate)Nmap done: 1 IP address (1 host up) scanned in 24.10 seconds