Packet Capture

The Device42 Packet Capture tool enables packet capture as a means of discovery. Packet capture discovers service communication happening in real-time for any service listeners known to Device42, letting you discover service communications that are too infrequent for scheduled discovery jobs to catch.

Device42 packet capture supports both individual and promiscuous interfaces, giving you the flexibility to deploy and use packet capture in the way that makes the most sense for your IT environment.

Prerequisites

You need the following to use the Device42 Packet Capture tool:

• A Device42 Main Appliance (MA).
• Network communication allowed from the machine you'll be capturing packets on to your Device42 MA.
• An active network adapter connected to the target traffic capture network.
• A packet capture library installed on your operating system:
  • On Windows, use a WinPcap-compatible library like Npcap. Be sure to select the Install in API-Compatible mode option during setup.
  • On Linux, use libpcap.

You can optionally enable promiscuous mode (also known as monitor mode) for the network or the interface of interest.

tip

Watch the Intro to Packet Capture video for a quick overview of how to set up and use packet capture with Device42.

Configure Packet Capture

1. Download the compressed d42-packet-capture.zip utility file and extract the contents to a directory of your choice.

2. Place the d42pcap.json config file into the directory with the utility.

3. On Linux, create a symlink for libpcap as required by the application, which searches for the filename libpcap.so.1:

   sudo ln -s /usr/lib/x86_64-linux-gnu/libpcap.so.1.8.1 /usr/lib/x86_64-linux-gnu/libpcap.so.1

   On Windows, no extra configuration is needed.

4. Configure the utility by editing the d42pcap.json file. At minimum, configure the following sections to run the Packet Capture utility:

   • Point the utility at your Device42 instance by entering its IP address, username, and password in the device42 section of the config file. Save the file.
   • Enter the name of your capture interface in the device property of the pcap section. Use the name as shown under ipconfig on Windows or ifconfig on Linux. For example, ens32.
   • Adjust the interval property of the common section. The default is to relay 60-second chunks of capture data to Device42 to avoid overwhelming the MA, especially if filtering isn't used or you're capturing traffic from many devices.

5. Optionally install the utility to run as a Windows or Linux service. See the Install Packet Capture as a System Service section.

Run the Packet Capture Utility

1. Ensure all Prerequisites are met.
2. Configure the utility as described in the Configure Packet Capture section above.
3. Execute the utility by running:
   • Windows: c:\> d42pcap.exe
   • Linux: $ sudo ./d42pcap_linux_64
4. Optionally configure the following runtime parameters:

Parameter	Description
list-devices	Lists all network adapters on the host
version	Prints the version of the utility
logs-dir	Overrides the directory to which log files are written
settings-dir	The directory containing the utility's JSON configuration file
settings-name	The name of the utility's JSON configuration file
debug	Turns on debug logging
install-win-service	Installs the utility as a Windows service (Windows executable only)
remove-win-service	Removes the utility from the installed Windows services (Windows executable only)

Configuration File Definitions

The configuration file contains the following sections:

Section	Description
device42	Contains settings required to interact with Device42.
common	Contains common application settings.
pcap	Contains settings that affect how raw network packets are handled.
capture	Settings that affect Device42 NetFlow and Packet Capture engine event processing. This section is intended for Device42 support.

Device42 Configuration

Property	Description	Required
Host	Base URL of the Device42 website	Yes
User	Username	Yes
Password	Password	Yes

Common Configuration

Property	Description	Required
Interval	The number of seconds to collect network events before sending to Device42	Yes
logs-dir	The directory to which log files are written	No

PCAP Configuration

Property	Description	Required
Device	Specify network capture interface	Yes
include-source-tcp-ports	TCP source ports to include	No
include-destination-tcp-ports	TCP destination ports to include	No
include-source-udp-ports	UDP source ports to include	No
include-destination-udp-ports	UDP destination ports to include	No
include-source-tcp-ips	TCP source IPs to include	No
include-dest-tcp-ips	TCP destination IPs to include	No
include-source-udp-ips	UDP source IPs to include	No
include-dest-udp-ips	UDP destination IPs to include	No
ignore-tcp	Ignore all TCP network events	No
ignore-udp	Ignore all UDP network events	No
promiscuous-mode	true captures all packets passed and received rather than just host packets	Yes
sniff-timeout	Duration in nanoseconds to wait for network events to be read (default: 2)	Yes
snap-length	Length of raw network packets to collect (default: 1600)	Yes

Capture Configuration

Property	Description	Required
live-entries	Display live entries	No
live-entries-ok	Display OK live entries	No
live-entries-nok	Display NOK live entries	No
print-data	Print data	No
ignore-ips	Ignored IPs	No
ignore-ports	Ignored ports	No
pass-to	Reserved for Device42 use	No
default-protocol	Reserved for Device42 use	No
only-stats	Reserved for Device42 use	No
report-any-ip	Reserved for Device42 use	No
report-src-ip	Reserved for Device42 use	No
report-dst-ip	Reserved for Device42 use	No
unprocessed-packets	Reserved for Device42 use	No

Install Packet Capture as a System Service

You can install the Packet Capture utility to run as a system service on Windows or Linux.

On Windows:

Execute with the install-win-service flag:

C:\> d42pcap -install-win-service

On Linux:

1. Create a service file in the /etc/systemd/system directory:

   [Unit]
   Description=Device42 Packet Capture Utility
   
   [Service]
   PIDFile=/tmp/d42pcap.pid
   User=root
   Group=root
   WorkingDirectory=/usr/bin
   ExecStart=/usr/bin/d42pcap
   Restart=always
   
   [Install]
   WantedBy=multi-user.target

2. Enable and start the service:

   sudo systemctl enable d42pcap.service
   sudo systemctl start d42pcap.service