linux - nmap 在针对本地主机以外的 ip 运行时显示较少的端口打开

Question

我在 vmware 工作站中有一个虚拟机，它是桥接网络和 DHCP。 DHCP 服务器分配的 IP 为 10.21.245.22。这是我的/etc/hosts 的样子:

127.0.0.1 hadoop-namenode-01 本地主机

我在盒子上运行命令 A 和 B。

命令 A:

root@hadoop-namenode-01:~# nmap -sT -sU -p- localhost

Starting Nmap 5.21 ( http://nmap.org ) at 2012-08-10 09:32 PDT
Nmap scan report for localhost (127.0.0.1)
Host is up (0.00029s latency).
rDNS record for 127.0.0.1: hadoop-namenode-01
Not shown: 131058 closed ports
PORT      STATE         SERVICE
22/tcp    open          ssh
53/tcp    open          domain
631/tcp   open          ipp
8020/tcp  open          unknown
9000/tcp  open          cslistener
9001/tcp  open          tor-orport
50070/tcp open          unknown
53/udp    open|filtered domain
68/udp    open|filtered dhcpc
123/udp   open          ntp
5353/udp  open|filtered zeroconf
47982/udp open|filtered unknown

Nmap done: 1 IP address (1 host up) scanned in 12.45 seconds

命令 B:

root@hadoop-namenode-01:~# nmap -sT -sU -p- 10.21.245.22

Starting Nmap 5.21 ( http://nmap.org ) at 2012-08-10 09:28 PDT
Nmap scan report for wn7x64-3jql0q1.dub.emea.dell.com (10.21.245.22)
Host is up (0.00029s latency).
Not shown: 131065 closed ports
PORT      STATE         SERVICE
22/tcp    open          ssh
68/udp    open|filtered dhcpc
123/udp   open          ntp
5353/udp  open|filtered zeroconf
47982/udp open|filtered unknown

Nmap done: 1 IP address (1 host up) scanned in 12.20 seconds

我的问题是:

因为我没有防火墙或类似的东西阻止端口，为什么 nmap 在针对 localhost 运行时显示更多端口打开，而在针对 ip 运行时显示较少端口。

Answer 1

why nmap shows more ports open when it's running against localhost while less ports are shown when it's running against the ip

一些应用程序决定只在本地主机(即 127.0.0.1)上显式监听(实际上是 bind)。您可以执行 netstat 来检查一下。