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netstat -nr

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 -n    Show network addresses as numbers (normally netstat interprets addresses and attempts to display them symbolically).  This option may be used with any
       of the display formats.
-r    Show the routing tables.  Use with -a to show protocol-cloned routes.  When -s is also present, show routing statistics instead.  When -l is also
       present, netstat assumes more columns are there and the maximum transmission unit.  More detailed information about the route metrics are displayed with
       -ll for TCP round trip times -lll for all metrics.  Use the -z flags to display only entries with non-zero RTT values.  (“mtu”) are also displayed.

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Routing tables

Internet:
Destination        Gateway            Flags               Netif Expire
default            192.168.xx.1       UGScg                 en0

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U = Up
G = Gateway
S = Static, e.g., default route added at boot time
H = Host-specific
C = Generate new (host-specific) routes on use
L = Valid link-layer (MAC) address
c = Cloned route
R = Reject route, known but unreachable route

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route get default

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应用程序
   ↓
路由表
   ↓
netif（网络接口）
   ↓
物理网卡 / 虚拟隧道
   ↓
网络