netstat
Linux Commands - Network Commands

netstat

Example: netstat -r This will display the routing table for your computer including: Destination, Gateway, Mask, Flags, and Interface. Options -r display routing table -i display interfaces -s display statistics The first example shows the routing table for a networked computer.

netstat -r


Kernel IP routing table

Destination Gateway Genmask Flags MSS Window irtt Iface

192.168.2.0 * 255.255.255.0 U 0 0 0 eth0

default 192.168.2.222 0.0.0.0 UG 0 0 0 eth0


The next example shows the interfaces.


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 20034 0 0 0 19150 0 0 0 BMRU

lo 16436 0 320359 0 0 0 320359 0 0 0 LRU


The last example shows statistics that can be handy for troubleshooting.


netstat -s

Ip:

340684 total packets received

0 forwarded

0 incoming packets discarded

339514 incoming packets delivered

339665 requests sent out

Icmp:

0 ICMP messages received

0 input ICMP message failed.

ICMP input histogram:

20 ICMP messages sent

0 ICMP messages failed

ICMP output histogram:

destination unreachable: 20

Tcp:

1121 active connections openings

5 passive connection openings

0 failed connection attempts

228 connection resets received

2 connections established

338456 segments received

338439 segments send out

43 segments retransmited

0 bad segments received.

191 resets sent

Udp:

1038 packets received

20 packets to unknown port received.

0 packet receive errors

1215 packets sent

TcpExt:

100 TCP sockets finished time wait in fast timer

22904 delayed acks sent

2 delayed acks further delayed because of locked socket

Quick ack mode was activated 21 times

134948 packets directly queued to recvmsg prequeue.

9313 of bytes directly received from backlog

4577720 of bytes directly received from prequeue

29032 packet headers predicted

118005 packets header predicted and directly queued to user

1955 acknowledgments not containing data received

146656 predicted acknowledgments

0 TCP data loss events

3 timeouts after reno fast retransmit

3 retransmits in slow start

23 other TCP timeouts

38 times receiver scheduled too late for direct processing

19 connections reset due to unexpected data

103 connections reset due to early user close

2 connections aborted due to timeout