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openSUSE 11.1 Reference Guide
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11.4 Networking

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
openSUSE 11.1 Reference Guide
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