需求是本地启动了oralce数据库和一个服务，连接的工具应用在pd的win7虚拟机中运行，如果访问127.0.0.1的话，只能访问虚拟机内部，如果想访问mac主机，在有网的情况下，NAT模式可以访问本机的外网IP。
但是这样有两个问题：
- 第一个随着网络的变化，要不停的修改连接地址。
- 如果没有网络连接，就不可连接。
初步查看了一下NAT的实现模式，实际上也是在本地建立了虚拟网络，然后对外访问的时候，屏蔽了内网的情况。
因此一般情况下虚拟机可以公共物理机的对外访问网络，但是外部无法访问虚拟机。但是网上有方法，就是配置NAT的端口映射，那么实际上，其实相当于和路由器相同的功能。
对于macOS来说，ParallelsDesktop(PD)虚拟机，并不像vmware在windows那样，就vmnet8这种虚拟网卡可以改。但是连接虚拟机的时候，如果是NAT模式，右上角就会显示虚拟机的IP，截图如下：
image.png
可见内部虚拟网络中，虚拟的IP是10.211.55.5
然后在mac的term中执行ifconfig
/Users/suitm>ifconfig
lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 16384
options=1203<RXCSUM,TXCSUM,TXSTATUS,SW_TIMESTAMP>
inet 127.0.0.1 netmask 0xff000000
inet6 ::1 prefixlen 128
inet6 fe80::1%lo0 prefixlen 64 scopeid 0x1
nd6 options=201<PERFORMNUD,DAD>
gif0: flags=8010<POINTOPOINT,MULTICAST> mtu 1280
stf0: flags=0<> mtu 1280
en5: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
ether ac:de:48:00:11:22
inet6 fe80::aede:48ff:fe00:1122%en5 prefixlen 64 scopeid 0x4
nd6 options=281<PERFORMNUD,INSECURE,DAD>
media: autoselect
status: active
en0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
ether 78:4f:43:75:21:0a
inet6 fe80::1848:803:28e7:badf%en0 prefixlen 64 secured scopeid 0x5
inet 192.168.31.203 netmask 0xffffff00 broadcast 192.168.31.255
nd6 options=201<PERFORMNUD,DAD>
media: autoselect
status: active
en2: flags=963<UP,BROADCAST,SMART,RUNNING,PROMISC,SIMPLEX> mtu 1500
options=60<TSO4,TSO6>
ether 92:00:c8:8a:b7:04
media: autoselect <full-duplex>
status: inactive
en4: flags=963<UP,BROADCAST,SMART,RUNNING,PROMISC,SIMPLEX> mtu 1500
options=60<TSO4,TSO6>
ether 92:00:c8:8a:b7:05
media: autoselect <full-duplex>
status: inactive
en1: flags=963<UP,BROADCAST,SMART,RUNNING,PROMISC,SIMPLEX> mtu 1500
options=60<TSO4,TSO6>
ether 92:00:c8:8a:b7:00
media: autoselect <full-duplex>
status: inactive
en3: flags=963<UP,BROADCAST,SMART,RUNNING,PROMISC,SIMPLEX> mtu 1500
options=60<TSO4,TSO6>
ether 92:00:c8:8a:b7:01
media: autoselect <full-duplex>
status: inactive
bridge0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
options=63<RXCSUM,TXCSUM,TSO4,TSO6>
ether 92:00:c8:8a:b7:00
Configuration:
id 0:0:0:0:0:0 priority 0 hellotime 0 fwddelay 0
maxage 0 holdcnt 0 proto stp maxaddr 100 timeout 1200
root id 0:0:0:0:0:0 priority 0 ifcost 0 port 0
ipfilter disabled flags 0x2
member: en1 flags=3<LEARNING,DISCOVER>
ifmaxaddr 0 port 8 priority 0 path cost 0
member: en2 flags=3<LEARNING,DISCOVER>
ifmaxaddr 0 port 6 priority 0 path cost 0
member: en3 flags=3<LEARNING,DISCOVER>
ifmaxaddr 0 port 9 priority 0 path cost 0
member: en4 flags=3<LEARNING,DISCOVER>
ifmaxaddr 0 port 7 priority 0 path cost 0
nd6 options=201<PERFORMNUD,DAD>
media: <unknown type>
status: inactive
p2p0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 2304
ether 0a:4f:43:75:21:0a
media: autoselect
status: inactive
awdl0: flags=8943<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> mtu 1484
ether 6a:10:9a:47:06:01
inet6 fe80::6810:9aff:fe47:601%awdl0 prefixlen 64 scopeid 0xc
nd6 options=201<PERFORMNUD,DAD>
media: autoselect
status: active
utun0: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 2000
inet6 fe80::8db7:12c6:559f:211f%utun0 prefixlen 64 scopeid 0xd
nd6 options=201<PERFORMNUD,DAD>
utun1: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 1380
inet6 fe80::ce4d:225c:38e2:af20%utun1 prefixlen 64 scopeid 0xe
nd6 options=201<PERFORMNUD,DAD>
vnic0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
options=3<RXCSUM,TXCSUM>
ether 00:1c:42:00:00:08
inet 10.211.55.2 netmask 0xffffff00 broadcast 10.211.55.255
media: autoselect
status: active
vnic1: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
options=3<RXCSUM,TXCSUM>
ether 00:1c:42:00:00:09
inet 10.37.129.2 netmask 0xffffff00 broadcast 10.37.129.255
media: autoselect
status: active
/Users/suitm>
直接用网络编辑器并不能看到，可以看，其中vnic0就是PD给NAT模式虚拟网络分配的本机IP。
因此，在NAT模式下，无论是否有网，都可以连接10.211.55.2 查出的这个地址，进行访问。
