11.4.1 Show the Network Status: netstat
netstat shows network connections, routing tables
(-r), interfaces (-i), masquerade
connections (-M), multicast memberships
(-g), and statistics (-s).
tux@mercury:~> netstat -r
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
192.168.2.0 * 255.255.254.0 U 0 0 0 eth0
link-local * 255.255.0.0 U 0 0 0 eth0
loopback * 255.0.0.0 U 0 0 0 lo
default 192.168.2.254 0.0.0.0 UG 0 0 0 eth0
tux@mercury:~> netstat -i
Kernel Interface table
Iface MTU Met RX-OK RX-ERR RX-DRP RX-OVR TX-OK TX-ERR TX-DRP TX-OVR Flg
eth0 1500 0 1624507 129056 0 0 7055 0 0 0 BMNRU
lo 16436 0 23728 0 0 0 23728 0 0 0 LRU
When displaying network connections or statistics, you can specify the
socket type to display: TCP (-t), UDP
(-u), or raw (-r). The
-p option shows the PID and name of the program to
which each socket belongs.
The following example lists all TCP connections and the programs using
these connections.
mercury:~ # netstat -t -p
Active Internet connections (w/o servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Pro
tcp 0 0 mercury:33513 www.novell.com:www-http ESTABLISHED 6862/fi
tcp 0 352 mercury:ssh mercury2.:trc-netpoll ESTABLISHED 19422/s
tcp 0 0 localhost:ssh localhost:17828 ESTABLISHED -
In the following, statistics for the TCP protocol are displayed:
tux@mercury:~> netstat -s -t
Tcp:
2427 active connections openings
2374 passive connection openings
0 failed connection attempts
0 connection resets received
1 connections established
27476 segments received
26786 segments send out
54 segments retransmited
0 bad segments received.
6 resets sent
[...]
TCPAbortOnLinger: 0
TCPAbortFailed: 0
TCPMemoryPressures: 0
