I have been trying to capture LLDP packets using tcpdump on my Ubuntu machine, but I am having some trouble. I have followed the code that was mentioned in the post (https://stackoverflow.com/questions/18095812/capture-lldp-packets-using-tcpdump), but for some reason it doesn’t seem to be working. I’ve tried different variations of the command, but nothing seems to be working.
Here’s the command that I’m using:
sudo tcpdump -vvvv -i eth0 -s 1500 -c 1 'ether[20:2] == 0x88cc'
I’ve also tried using just
sudo tcpdump without any options, but still no success. Could anyone tell me what I’m doing wrong? Is there an issue with my command? Or is there something I need to install or configure on my machine to make it work?
One thing that I’ve noticed is that when I run the command, it seems to just hang indefinitely without producing any output. I’m not sure if this is normal or not. Any help would be greatly appreciated. Thank you!
Hello there! I see you’re interested in capturing LLDP packets using tcpdump. This can be a bit tricky, but with the right approach, you can make it work.
First and foremost, ensure that you have tcpdump installed and properly configured on your system. You can do this by running the command “sudo apt-get install tcpdump” if you’re on a Debian-based system. Once done, you’ll need to configure tcpdump to capture LLDP packets by using the following command:
sudo tcpdump -i eth0 -vvv -s 1500 '(ether[12:2]=0x88cc or ether[20:2]=0x88cc)'
In this command, we’re telling tcpdump to capture LLDP packets on interface eth0 by filtering the results with the ether[12:2]=0x88cc or ether[20:2]=0x88cc parameters, which are the OUIs for LLDP frames. We’re also setting the verbosity level to 3 (-vvv) and the snapshot length to 1500 (-s 1500) for better packet capture.
Once you run this command, you should start seeing LLDP packets being captured in the output. You can further refine your results by filtering for specific information within the LLDP packets, such as system name or port information, by using the following command:
sudo tcpdump -i eth0 -vvv -s 1500 '(ether[12:2]=0x88cc or ether[20:2]=0x88cc) and (ether[14:2]=0x0006)'
In this command, we’re adding an additional filter to capture only LLDP frames that contain the port sub-type (0x0006) in the TLVs. This can help you identify which ports on your network are sending or receiving LLDP packets, as well as the associated VLAN ID and other useful information.
In summary, capturing LLDP packets using tcpdump can be a bit challenging, but with the right approach and filters, you can get the results you need. Remember to configure tcpdump properly, filter for LLDP frames, and refine your results with additional filters as needed. Good luck!
One possible solution for capturing LLDP packets using tcpdump is to use the following command: `sudo tcpdump -i eth0 -vv -s 1500 ‘(ether[12:2]=0x88cc or ether[20:2]=0x2000)’`. This command will capture all LLDP packets on the eth0 interface and display them in verbose mode.
It’s important to note that the `-s` flag specifies the snapshot length, which should be set high enough to capture the entire packet. Additionally, the `ether[12:2]` and `ether[20:2]` parameters are used to filter the packets by the LLDP Ethernet Type (0x88cc) and the LLDP Subtype Organizationally Unique Identifier (0x2000), respectively.
It’s worth mentioning that tcpdump is a powerful tool for capturing and analyzing network packets, and there are many different ways to use it depending on your specific needs. If you have any further questions or concerns regarding capturing LLDP packets with tcpdump, feel free to ask.
When using tcpdump to capture LLDP packets, make sure to include the -vv option to ensure that you capture all packets with the most detailed output. This will give you the necessary information about the ports and the devices connected to them. It would also be helpful to use a filter to capture only the desired packets, such as `-f lldp`.
In addition, consider using a tool that is specifically designed to capture LLDP packets, such as lldpd or ladvd. These tools make it easier to capture and analyze LLDP packets and extract the relevant information in a more concise format.
It’s also important to keep in mind that not all devices support LLDP, so you may not be able to capture all relevant information. If you are having trouble capturing LLDP packets from a specific device, it may be worth checking the device’s specifications or contacting the manufacturer for support.
Overall, capturing LLDP packets can be a valuable tool for network analysis and troubleshooting, but it’s important to use the right tools and filters to ensure accurate and complete data capture.
To capture LLDP packets using tcpdump, you can use the following command:
sudo tcpdump -nn -i eth0 -v -c 1 ether proto 0x88cc
This command will capture and display the first LLDP packet received on the interface `eth0`. The `-nn` option specifies that tcpdump should display numeric values instead of resolving host names and port numbers. The `-i` option specifies the interface to listen on. The `-v` option specifies that tcpdump should display verbose output. The `-c 1` option specifies that tcpdump should capture only one packet. Finally, the `ether proto 0x88cc` filter specifies that only packets with the ethertype of LLDP should be captured.
I have extensive experience using tcpdump to capture and analyze packets in network troubleshooting scenarios. This command is a reliable way to capture LLDP packets, which can be useful for network mapping and discovery. Keep in mind that tcpdump captures packets in real-time, so if there is a high volume of traffic on the network, you may need to use additional filters to narrow down the captured packet stream.