How can I monitor LAN traffic on raspberry pi?

Question

I am trying to build a local network consisting of around 10-25 raspberry pis, each running on a static ip address. I wonder how I can monitor the traffic in the network. To be specific is there any tool I can use to monitor incoming and outgoing packets without generating extra network traffic?

Thanks a lot!

edit: Sorry that I might not have explained my question clearly. I am building an adhoc network with Pis only, no router. Each Pi communicates directly with other Pis. I want each Pi to monitor its own incoming and outgoing traffic to other Pis.

Answer 1

Probably the most popular related project with GUI is Wireshark

Wireshark is the world’s foremost and widely-used network protocol analyzer. It lets you see what’s happening on your network at a microscopic level and is the de facto (and often de jure) standard across many commercial and non-profit enterprises, government agencies, and educational institutions. Wireshark development thrives thanks to the volunteer contributions of networking experts around the globe and is the continuation of a project started by Gerald Combs in 1998.

sudo apt-get install wireshark

And without GUI you have tshark used by wireshark.

TShark is a network protocol analyzer. It lets you capture packet data from a live network, or read packets from a previously saved capture file, either printing a decoded form of those packets to the standard output or writing the packets to a file. TShark's native capture file format is pcapng format, which is also the format used by wireshark and various other tools.

sudo apt-get install tshark

Answer 2

You can use tcpdump too. It may already be installed on your distro. It depends on how far you want to go into the analysis of captured packets.