我在VirtualBox 4.2.4中设置的12.04主机上安装了Ubuntu 12.04vm
– 桥接网络模式
– 混杂允许所有

当我尝试从任何网络客户端ping虚拟客户端时,我得到了预期的结果.

PING 192.168.1.209 (192.168.1.209) 56(84) bytes of data.
64 bytes from 192.168.1.209: icmp_req=1 ttl=64 time=0.427 ms
...

vm内的Internet访问是正常的

但是,当我对它进行nmap时,我就没有了！

jeremy@bangkok:~$nmap -sV -p 1-65535 192.168.1.209
Starting Nmap 5.21 ( http://nmap.org ) at 2012-11-15 18:39 CST
Nmap scan report for jeremy (192.168.1.209)
Host is up (0.0032s latency).
All 65535 scanned ports on jeremy (192.168.1.209) are closed
Service detection performed. Please report any incorrect results at http://nmap.org/submit/
Nmap done: 1 IP address (1 host up) scanned in 0.88 seconds

VM上的ufw和iptables ……

jeremy@jeremy:~$sudo service ufw stop
[sudo] password for jeremy: 
ufw stop/waiting
jeremy@jeremy:~$sudo iptables -L
Chain INPUT (policy ACCEPT)
target     prot opt source               destination         

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination         

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination

我已经扫描过并且没有理由相信我的路由器阻塞了内部端口.

jeremy@bangkok:~$nmap -v 192.168.1.2

Starting Nmap 5.21 ( http://nmap.org ) at 2012-11-15 18:44 CST
Initiating Ping Scan at 18:44
Scanning 192.168.1.2 [2 ports]
Completed Ping Scan at 18:44,0.00s elapsed (1 total hosts)
Initiating Parallel DNS resolution of 1 host. at 18:44
Completed Parallel DNS resolution of 1 host. at 18:44,0.03s elapsed
Initiating Connect Scan at 18:44
Scanning 192.168.1.2 [1000 ports]
Discovered open port 445/tcp on 192.168.1.2
Discovered open port 139/tcp on 192.168.1.2
Discovered open port 3306/tcp on 192.168.1.2
Discovered open port 80/tcp on 192.168.1.2
Discovered open port 111/tcp on 192.168.1.2
Discovered open port 53/tcp on 192.168.1.2
Discovered open port 5902/tcp on 192.168.1.2
Discovered open port 8090/tcp on 192.168.1.2
Discovered open port 6881/tcp on 192.168.1.2
Completed Connect Scan at 18:44,0.02s elapsed (1000 total ports)
Nmap scan report for 192.168.1.2
Host is up (0.0017s latency).
Not shown: 991 closed ports
PORT     STATE SERVICE
53/tcp   open  domain
80/tcp   open  http
111/tcp  open  rpcbind
139/tcp  open  netbios-ssn
445/tcp  open  microsoft-ds
3306/tcp open  MysqL
5902/tcp open  vnc-2
6881/tcp open  bittorrent-tracker
8090/tcp open  unknown

Read data files from: /usr/share/nmap
Nmap done: 1 IP address (1 host up) scanned in 0.08 seconds

回答…
原来所有的端口都对网络开放了.我安装了开放的ssh并确认了它.然后我编辑了我的db conf来听外部IP,一切都很顺利.