Linux® Routing

netstat

netstat, short for network statistics, is a command for displaying network information on the local node. The most common use of netstat is to display the route table:

[root@lefty /root]# netstat -r 
Kernel IP routing table 
Destination     Gateway       Genmask         Flags MSS Window irtt Iface 
lefty           *             255.255.255.255 UH      0 0         0 eth0 
192.168.1.0     *             255.255.255.0   U       0 0         0 eth0 
127.0.0.0       *             255.0.0.0       U       0 0         0 lo 
default         192.168.1.1   0.0.0.0         UG      0 0         0 eth0 

There is much more to netstat than simply printing the routing table. In fact, most of netstat’s output shows network connections on the local node.

-a

The -a, or “all” parameter tells netstat to print all open sockets on the local node. This includes any connections initiated from the local node or daemons ...