GCIH · Question #793
What does the term any instruct tcpdump to capture in the following command? tcpdump -A -i any 'port 21 && host 192.168.100.1'
The correct answer is A. Network Interface. In tcpdump, the -i flag designates the network interface to capture on, and 'any' is a special pseudo-interface that captures traffic across all available interfaces simultaneously.
Question
What does the term any instruct tcpdump to capture in the following command? tcpdump -A -i any 'port 21 && host 192.168.100.1'
Options
- ANetwork Interface
- BIP address
- CPort
- DProtocol
How the community answered
(54 responses)- A94% (51)
- B4% (2)
- D2% (1)
Why each option
In tcpdump, the -i flag designates the network interface to capture on, and 'any' is a special pseudo-interface that captures traffic across all available interfaces simultaneously.
The -i flag in tcpdump specifies which network interface to listen on for packet capture. The argument 'any' is a special pseudo-interface recognized by tcpdump that instructs it to listen on all available network interfaces at once. This is useful when traffic may enter or leave through multiple interfaces and the exact path is unknown.
The IP address in this command is specified by the 'host 192.168.100.1' expression in the BPF filter string, not by the 'any' argument.
The port is defined by 'port 21' in the BPF filter expression, which is entirely separate from the -i interface argument.
Protocol selection in tcpdump is done via filter keywords such as 'tcp' or 'udp' in the BPF expression; 'any' following -i has no relation to protocol filtering.
Concept tested: tcpdump -i any interface capture option
Source: https://www.tcpdump.org/manpages/tcpdump.1.html
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