Configure Ethernet Port IP Address on Linux Notebook Running Wireshark for Passive Tap

Configure Ethernet Port IP Address on Linux Notebook Running Wireshark Passive Tap

This article covers how to configure the Ethernet port IP address on a Linux notebook that is running Wireshark in passive tap mode. Specifically, we will look at how to set up a 100 Mb/s Ethernet link using the ethtap interface, which provides one-way Ethernet tunneling.

What is Wireshark and why use Passive Tap?

Wireshark is a popular open-source packet analyzer that can be used to troubleshoot network issues, analyze network traffic, and develop network applications. The tool can capture and display packets in real-time, providing detailed information about each packet.

Passive tap mode is a way of monitoring network traffic without interfering with the traffic itself. It allows Wireshark to capture traffic from a network interface, but without sending any packets on the interface. This is particularly useful when you want to monitor the traffic without disrupting the network flow or revealing your presence.

One of the ways to set up a passive tap in Wireshark is by using the ethtap interface, which allows for one-way Ethernet tunneling. This means that you can create a virtual interface that receives traffic from one interface and forwards it to another interface.

Setting up a 100 Mb/s Ethernet Link using ethtap

To set up a 100 Mb/s Ethernet link using the ethtap interface, you need to follow these steps:

1. Connect the Linux laptop to the Ethernet port using an RJ-45 eth1 adapter plugged into a USB port.
2. Check the interface name using the command:
ifconfig
3. Create a tap device using the command:
sudo apt-get install ethtool
sudo tunctl -t mytap
ifconfig mytap up
ethtool -s mytap speed 100 duplex full autoneg off
4. Set up the ethtap interface using the command:
sudo ethtool -K eth1 rx on
sudo ethtool -n eth1 tap:mytap tx_ntuple off
sudo ethtool -i eth1 | grep driver
5. Configure the IP address of the interface using the command:
sudo ifconfig eth1 netmask up

Note that you should replace and with the actual IP address and netmask that you want to use. This configuration will create a virtual interface called mytap that receives traffic from eth1 and forwards it to the network, with a speed of 100 Mb/s.

Using Wireshark with the Passive Tap

To use Wireshark with the passive tap configuration, you need to follow these steps:

1. Start Wireshark with the command:
sudo wireshark
2. Select the ethtap interface using the interface selection dialog.
3. Start capturing packets using the "Capture" button.
4. Stop capturing packets using the "Stop" button.
5. Analyze the captured packets using Wireshark's display filters and other features.

References

• Wireshark: Setting up a Passive Tap https://wiki.wireshark.org/CaptureSetup/PassiveTap
• ethtool man page https://linux.die.net/man/8/ethtool
• Wireshark: ethtap Interfaces https://wiki.wireshark.org/CaptureSetup/