TCPDump

Looking at the packets.

Using TCPDump to capture all traffic going into and out of an interface on Linux:

sudo tcpdump -w issue.pcap -i eth0

You might need to change the interface name in the above command if you're interface is named differently. This command will list all available interfaces; pick the right one (not the loop-back interface):

ip link show

Run the above tcpdump command on the FOG machine, then start the remote target host. Wait until the remote target host fails, then stop tcpdump using ctrl+c. Then transfer the PCAP file to your PC and examine it using Wireshark.

You may get the issue.pcap file by a number of means. The most basic way is by placing the pcap file inside of the /tftpboot directory (or saving it there) and then using TFTP to transfer the file to a Windows machine.

This would save the file to your /tftpboot directory, but you still need to specify the correct interface:

sudo tcpdump -w /tftpboot/issue.pcap -i eth0

Then on a windows machine, you would issue this command to retrieve the file via TFTP:

tftp –i x.x.x.x get issue.pcap

Obviously you need the TFTP windows component installed, and you should turn off your windows firewall. Details about those things can be found here:

Troubleshoot_TFTP

After the capture is completed and you've opened the PCAP file, please use the MAC address of the target host as the filter for sender & receiver. The below example filter basically does this: ( Show packet if Sending MAC equals xxxxxxx OR Receiving MAC equals xxxxxx )

Example Filter (change the MAC addresses):

eth.dst == 00:0C:CC:76:4E:07 || eth.src==00:0C:CC:76:4E:07

Other usefull display filters are bootp (DHCP), tftp and http!