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Linux tcpdump command

Linux command Daquan Linux command Daquan

Linux tcpdump command is used to dump the data transmission network.

Execute tcpdump command lists via packet header specifies the network interface in the Linux operating system, you must be a system administrator.

grammar 

tcpdump [-adeflnNOpqStvx][-c<数据包数目>][-dd][-ddd][-F<表达文件>][-i<网络界面>][-r<数据包文件>][-s<数据包大小>][-tt][-T<数据包类型>][-vv][-w<数据包文件>][输出数据栏位]

Parameter Description:

  • -a try to network and broadcast addresses into names.
  • After -c <packet number> Specifies the number of packets received, stop dumping operations.
  • -d The compiled data packets encoded converted into readable format and dumped to the standard output.
  • -dd the compiled data packet encoding format is converted into the C language, and dumped to the standard output.
  • -ddd the compiled data packet is converted into coded decimal format and dumped to the standard output.
  • -e Displays the connection-level header on each column of data dump.
  • -f Displays Internet addresses using the number.
  • -F <File expression> Specifies the file containing the means of expression.
  • -i <network interface> Use specified network sectional send packets.
  • -l use the buffer to standard output columns.
  • -n do not host network addresses into names.
  • -N Do not list the domain name.
  • -O Not encoded packet optimization.
  • -p let the network interface into promiscuous mode.
  • -q fast output, to list only a few transmission protocol information.
  • -r <package file> reads the packet data from the specified file.
  • -s <packet size> Sets the size of each packet.
  • -S Absolute rather than relative value of the number of associations listed in TCP.
  • -t does not display the time stamp on each column of data dump.
  • -tt display unformatted timestamp on each column of data dump.
  • -T <Packet type> to force the expression specified data packet translated packet type settings.
  • -v displays detailed instruction execution.
  • -vv show more detailed instruction execution.
  • -x hexadecimal character code listed in the packet data.
  • -w <package file> write packet data to the specified file.

Examples

The 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 1:25(24) ack 118 win 32768
23:35:56.242812 PPPoE [ses 0x1cb0] IP 118.250.6.85.64120 > 115.238.1.45.3724: P 1:25(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 received by filter
0 packets dropped by kernel

Displays the number of packets 

# 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 received by filter
129 packets dropped by kernel

Compact display 

# tcpdump -c 10 -q //精简模式显示 10个包
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 received by filter
0 packets dropped by kernel

Convert grams to read format 

# tcpdump -d    
(000) ret   #96

Converted to decimal format 

# tcpdump -ddd
1
6 0 0 96

Linux command Daquan Linux command Daquan