Simple packet capture Analysis in linux
Sometimes we may encounter some problems that require packet capture analysis. When there is no professional packet capture tool at hand, we can use tcpdump instead (this tool is provided in general releases)
For example, we need to analyze the packet sending status of port 22 of the destination IP address 192.168.7.188 under the eth0 interface.
Tcpdump-I eth0 dst 192.168.7.188 and port 22
Tcpdump-I eth0 dst 192.168.7.188 and port 22
Tcpdump: verbose output suppressed, use-v or-vv for full protocol decode
Listening on eth0, link-type EN10MB (Ethernet), capture size 65535 bytes
16:51:55. 861670 IP 192.168.7.26.ssh> 192.168.7.188.37540: Flags [P.], seq 2209699250: 2209699442, ack 582840950, win 249, options [nop, nop, TS val 428468844 ecr 517889], length 192
16:51:55. 868590 IP 192.168.7.26.ssh> 192.168.7.188.37540: Flags [P.], seq 192: 416, ack 1, win 249, options [nop, nop, TS val 428468851 ecr 517897], length 224
16:51:55. 870577 IP 192.168.7.26.ssh> 192.168.7.188.37540: Flags [P.], seq 416: 624, ack 1, win 249, options [nop, nop, TS val 428468853 ecr 517899], length 208
16:51:55. 872602 IP 192.168.7.26.ssh> 192.168.7.188.37540: Flags [P.], seq 624: 832, ack 1, win 249, options [nop, nop, TS val 428468855 ecr 517899], length 208
16:51:55. 874576 IP 192.168.7.26.ssh> 192.168.7.188.37540: Flags [P.], seq 832: 1040, ack 1, win 249, options [nop, nop, TS val 428468857 ecr 517900], length 208
16:51:55. 876573 IP 192.168.7.26.ssh> 192.168.7.188.37540: Flags [P.], seq 1040: 1248, ack 1, win 249, options [nop, nop, TS val 428468859 ecr 517900], length 208
16:51:55. 878574 IP 192.168.7.26.ssh> 192.168.7.188.37540: Flags [P.], seq 1248: 1456, ack 1, win 249, options [nop, nop, TS val 428468861 ecr 517901], length 208
16:51:55. 880574 IP 192.168.7.26.ssh> 192.168.7.188.37540: Flags [P.], seq 1456: 1664, ack 1, win 249, options [nop, nop, TS val 428468863 ecr 517901], length 208