Linux tcpdump command details how to use the Linux tcpdump command

Source: Internet
Author: User
Tags ack dns2 ssh nxdomain

Run the tcpdump command to list the packet headers that pass through the specified network. In Linux, you must be a system administrator.

Syntax

Tcpdump [-adeflnNOpqStvx] [-c <number of packets>] [-dd] [-ddd] [-F <File expression>] [-I <network interface>]

[-R <data packet File>] [-s <data packet size>] [-tt] [-T <data packet type>] [-vv] [-w <data packet File>] [output data column]

Parameter description:

  • -A tries to convert the network and broadcast address to a name.

  • -C

    <Number of data packets> after receiving the specified number of data packets, the dumping operation is stopped.

  • -D converts compiled data packet encoding into a readable format and dumps it to standard output.

  • -Dd converts the compiled data packet encoding to the C language format and dumps it to the standard output.

  • -Ddd converts the compiled data packet encoding to a decimal number format and dumps it to the standard output.

  • -E displays the connection level file header on each column of dumped data.

  • -F displays the internet address in numbers.

  • -F

    <Expression File> specify the file containing the expression.

  • -I

    <Network interface> send data packets using the specified network section.

  • -L use the buffer of the standard output column.

  • -N does not convert the network address of the host into a name.

  • -N does not list domain names.

  • -O does not optimize packet encoding.

  • -P prevents the network interface from entering the hybrid mode.

  • -Q: fast output. Only a few transmission protocol information are listed.

  • -R

    <Packet File> read data from the specified file.

  • -S

    <Packet size> set the size of each packet.

  • -S: use absolute rather than relative values to list the number of TCP connections.

  • -T the time stamp is not displayed on the dumped data in each column.

  • -Tt displays unformatted timestamps on the dumped data in each column.

  • -T

    <Data packet type> forcibly translate the data packet specified by the expression into the set data packet type.

  • -V displays the instruction execution process in detail.

  • -Vv: displays the instruction execution process in detail.

  • -X uses a hexadecimal code to list data packets.

  • -W

    <Data packet File> write the data packet to the specified file.

Instance

Show TCP packet information

# Tcpdump

Tcpdump: verbose output suppressed, use-v or-vv for full protocol decode listening on eth0, link-type EN10MB (Ethernet), capture size 96 bytes

23:35:55. 129998 IP 192.168.0.3.ssh> 192.168.0.1.2101: P 148872068: 148872168 (100) ack 4184371747 win 2100

23:35:55. 182357 IP 192.168.0.1.2101> 192.168.0.3.ssh:. ack 100 win 64240

23:35:55. 182397 IP 192.168.0.3.ssh> 192.168.0.1.2101: P 100:200 (100) ack 1 win 2100

23:35:55. 131713 IP 192.168.0.3.32804> dns2.cs.hn.cn. domain: 50226 + PTR? 1.0.168.192.in-addr. arpa. (42)

23:35:55. 131896 PPPoE [ses 0x1cb0] IP 118.250.6.85.64215> dns2.cs.hn.cn. domain: 50226 + PTR? 1.0.168.192.in-addr. arpa. (42)

23:35:55. 154238 PPPoE [ses 0x1cb0] IP dns2.cs.hn.cn. domain> 118.250.6.85.64215: 50226 NXDomain 0/0/0 (42)

23:35:55. 156298 IP dns2.cs.hn.cn. domain> 192.168.0.3.32804: 50226 NXDomain 0/0/0 (42)

23:35:55. 159292 IP 192.168.0.3.32804> dns2.cs.hn.cn. domain: 30304 + PTR? 3.0.168.192.in-addr. arpa. (42)

23:35:55. 159449 PPPoE [ses 0x1cb0] IP 118.250.6.85.64215> dns2.cs.hn.cn. domain: 30304 + PTR? 3.0.168.192.in-addr. arpa. (42)

23:35:55. 179816 PPPoE [ses 0x1cb0] IP dns2.cs.hn.cn. domain> 118.250.6.85.64215: 30304 NXDomain 0/0/0 (42)

23:35:55. 181279 IP dns2.cs.hn.cn. domain> 192.168.0.3.32804: 30304 NXDomain 0/0/0 (42)

23:35:55. 181806 IP 192.168.0.3.ssh> 192.168.0.1.2101: P 200: 268 (68) ack 1 win 2100

23:35:55. 182177 IP 192.168.0.1.2101> 192.168.0.3.ssh:. ack 268 win 64198

23:35:55. 182677 IP 192.168.0.3.32804> dns2.cs.hn.cn. domain: 43983 + PTR? 112.96.103.202.in-addr. arpa. (45)

23:35:55. 182807 PPPoE [ses 0x1cb0] IP 118.250.6.85.64215> dns2.cs.hn.cn. domain: 43983 + PTR? 112.96.103.202.in-addr. arpa. (45)

23:35:55. 183055 IP 192.168.0.3.ssh> 192.168.0.1.2101: P 268: 352 (84) ack 1 win 2100

23:35:55. 201096 PPPoE [ses 0x1cb0] IP dns2.cs.hn.cn. domain> 118.250.6.85.64215: 43983 1/0/0 (72)

23:35:55. 203087 IP dns2.cs.hn.cn. domain> 192.168.0.3.32804: 43983 1/0/0 (72)

23:35:55. 204666 IP 192.168.0.3.ssh> 192.168.0.1.2101: P 352: 452 (100) ack 1 win 2100

23:35:55. 204852 IP 192.168.0.1.2101> 192.168.0.3.ssh:. ack 452 win 64152

23:35:55. 205305 IP 192.168.0.3.ssh> 192.168.0.1.2101: P 452: 520 (68) ack 1 win 2100

23:35:55. 205889 IP 192.168.0.3.32804> dns2.cs.hn.cn. domain: 9318 + PTR? 85.6.250.118.in-addr. arpa. (43)

23:35:55. 206071 PPPoE [ses 0x1cb0] IP 118.250.6.85.64215> dns2.cs.hn.cn. domain: 9318 + PTR? 85.6.250.118.in-addr. arpa. (43)

23:35:55. 215338 PPPoE [ses 0x1cb0] IP 115.238.1.45.3724> 118.250.6.85.64120: P 2392751922: 2392751987 (65) ack 2849759785 win 54

23:35:55. 216273 IP 115.238.1.45.3724> 192.168.0.65.2057: P 2392751922: 2392751987 (65) ack 2849759785 win 54

23:35:55. 329204 IP 192.168.0.1.2101> 192.168.0.3.ssh:. ack 520 win 64135

23:35:55. 458214 IP 192.168.0.65.2057> 115.238.1.45.3724:. ack 65 win 32590

23:35:55. 458221 PPPoE [ses 0x1cb0] IP 118.250.6.85.64120> 115.238.1.45.3724:. ack 65 win 32590

23:35:55. 708228 PPPoE [ses 0x1cb0] IP 115.238.1.45.3724> 118.250.6.85.64120: P 65: 118 (53) ack 1 win 54

23:35:55. 710213 IP 115.238.1.45.3724> 192.168.0.65.2057: P 65: 118 (53) ack 1 win 54

23:35:55. 865151 IP 192.168.0.65.2057> 115.238.1.45.3724:. ack 118 win 32768

23:35:55. 865157 PPPoE [ses 0x1cb0] IP 118.250.6.85.64120> 115.238.1.45.3724:. ack 118 win 32768

23:35:56. 242805 IP 192.168.0.65.2057> 115.238.1.45.3724: P (24) ack 118 win 32768

23:35:56. 242812 PPPoE [ses 0x1cb0] IP 118.250.6.85.64120> 115.238.1.45.3724: P (24) ack 118 win 32768

23:35:56. 276816 PPPoE [ses 0x1cb0] IP 115.238.1.45.3724> 118.250.6.85.64120:. ack 25 win 54

23:35:56. 278240 IP 115.238.1.45.3724> 192.168.0.65.2057:. ack 25 win 54

23:35:56. 349747 PPPoE [ses 0x1cb0] IP 115.238.1.45.3724> 118.250.6.85.64120: P 118:159 (41) ack 25 win 54

23:35:56. 351780 IP 115.238.1.45.3724> 192.168.0.65.2057: P 118:159 (41) ack 25 win 54

23:35:56. 400051 PPPoE [ses 0x1cb0] IP 119.147.18.44.8000> 118.250.6.85.4000: UDP, length 79

23:35:56. 475050 IP 192.168.0.65.2057> 115.238.1.45.3724:. ack 159 win 32762

23:35:56. 475063 PPPoE [ses 0x1cb0] IP 118.250.6.85.64120> 115.238.1.45.3724:. ack 159 win 32762

23:35:56. 508968 PPPoE [ses 0x1cb0] IP 115.238.1.45.3724> 118.250.6.85.64120: P 159: 411 (252) ack 25 win 54

23:35:56. 510182 IP 115.238.1.45.3724> 192.168.0.65.2057: P 159: 411 (252) ack 25 win 54

23:35:56. 592028 PPPoE [ses 0x1cb0] IP 117.136.2.43.38959> 118.250.6.85.63283: UDP, length 36

44 packets captured

76 packets partitioned ed by filter

0 packets dropped by kernel

Displays a specified number of packages

# Tcpdump-c 20

Tcpdump: verbose output suppressed, use-v or-vv for full protocol decode

Listening on eth0, link-type EN10MB (Ethernet), capture size 96 bytes

23:36:28. 949538 IP 192.168.0.3.ssh> 192.168.0.1.2101: P 148875984: 148876020 (36) ack 4184373187 win 2100

23:36:28. 994325 IP 192.168.0.1.2101> 192.168.0.3.ssh:. ack 36 win 64020

23:36:28. 994368 IP 192.168.0.3.ssh> 192.168.0.1.2101: P 36: 72 (36) ack 1 win 2100

23:36:28. 950779 IP 192.168.0.3.32804> dns2.cs.hn.cn. domain: 18242 + PTR? 1.0.168.192.in-addr. arpa. (42)

23:36:28. 950948 PPPoE [ses 0x1cb0] IP 118.250.6.85.64215> dns2.cs.hn.cn. domain: 18242 + PTR? 1.0.168.192.in-addr. arpa. (42)

23:36:28. 960105 PPPoE [ses 0x1cb0] IP 222.82.119.41.13594> 118.250.6.85.63283: UDP, length 36

23:36:28. 962192 IP 222.82.119.41.13594> 192.168.0.65.13965: UDP, length 36

23:36:28. 963118 IP 192.168.0.65.13965> 222.82.119.41.13594: UDP, length 34

23:36:28. 963123 PPPoE [ses 0x1cb0] IP 118.250.6.85.63283> 222.82.119.41.13594: UDP, length 34

23:36:28. 970185 PPPoE [ses 0x1cb0] IP dns2.cs.hn.cn. domain> 118.250.6.85.64215: 18242 NXDomain 0/0/0 (42)

23:36:28. 970413 IP dns2.cs.hn.cn. domain> 192.168.0.3.32804: 18242 NXDomain 0/0/0 (42)

23:36:28. 972352 IP 192.168.0.3.32804> dns2.cs.hn.cn. domain: 17862 + PTR? 3.0.168.192.in-addr. arpa. (42)

23:36:28. 972474 PPPoE [ses 0x1cb0] IP 118.250.6.85.64215> dns2.cs.hn.cn. domain: 17862 + PTR? 3.0.168.192.in-addr. arpa. (42)

23:36:28. 982287 PPPoE [ses 0x1cb0] IP 121.12.131.163.13109> 118.250.6.85.63283: UDP, length 27

23:36:28. 984162 IP 121.12.131.163.13109> 192.168.0.65.13965: UDP, length 27

23:36:28. 985021 IP 192.168.0.65.13965> 121.12.131.163.13109: UDP, length 103

23:36:28. 985027 PPPoE [ses 0x1cb0] IP 118.250.6.85.63283> 121.12.131.163.13109: UDP, length 103

23:36:28. 991919 PPPoE [ses 0x1cb0] IP dns2.cs.hn.cn. domain> 118.250.6.85.64215: 17862 NXDomain 0/0/0 (42)

23:36:28. 993142 IP dns2.cs.hn.cn. domain> 192.168.0.3.32804: 17862 NXDomain 0/0/0 (42)

23:36:28. 993574 IP 192.168.0.3.ssh> 192.168.0.1.2101: P 72: 140 (68) ack 1 win 2100

20 packets captured

206 packets partitioned ed by filter

129 packets dropped by kernel

Simplified display

# Tcpdump-c 10-q // 10 packages are displayed in simplified mode

Tcpdump: verbose output suppressed, use-v or-vv for full protocol decode

Listening on eth0, link-type EN10MB (Ethernet), capture size 96 bytes

23:43:05. 792280 IP 192.168.0.3.ssh> 192.168.0.1.2101: tcp 36

23:43:05. 842115 IP 192.168.0.1.2101> 192.168.0.3.ssh: tcp 0

23:43:05. 845074 IP 115.238.1.45.3724> 192.168.0.65.2057: tcp 0

23:43:05. 907155 IP 192.168.0.3.ssh> 192.168.0.1.2101: tcp 36

23:43:05. 793880 IP 192.168.0.3.32804> dns2.cs.hn.cn. domain: UDP, length 42

23:43:05. 794076 PPPoE [ses 0x1cb0] IP 118.250.6.85.64219> dns2.cs.hn.cn. domain: UDP, length 42

23:43:05. 811127 PPPoE [ses 0x1cb0] IP dns2.cs.hn.cn. domain> 118.250.6.85.64219: UDP, length 42

23:43:05. 814764 IP dns2.cs.hn.cn. domain> 192.168.0.3.32804: UDP, length 42

23:43:05. 816404 IP 192.168.0.3.32804> dns2.cs.hn.cn. domain: UDP, length 42

23:43:05. 816545 PPPoE [ses 0x1cb0] IP 118.250.6.85.64219> dns2.cs.hn.cn. domain: UDP, length 42

10 packets captured

39 packets partitioned ed by filter

0 packets dropped by kernel

Convert G reading format

# Tcpdump-d

(000) ret #96

Convert to decimal format

# Tcpdump-ddd

1

6 0 0 96

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