The simplest and most efficient way to check all dropped packets in real time is C. fw ctl zdebug + drop in expert mode. This command is a shortcut command that sets the kernel debug flags to a predefined value and prints the debug output to the standard output. It is useful for general debugging of common issues, such as traffic drops, NAT, VPN, or clustering. It has a small buffer size and does not require additional steps to start or stop the debugging. However, it has some limitations, such as it cannot be used with SecureXL, it cannot filter the output by chain modules, and it cannot save the output to a file12.
The other commands are not as simple or efficient as the fw ctl zdebug + drop command. The command tail -f $FWDIR/log/fw.log |grep drop in expert mode will only show the drops that are logged in the fw.log file, which may not include all the drops that occur in the kernel. The command cat /dev/fw1/log in expert mode will show the raw binary data of the kernel debug buffer, which is not human-readable and may contain irrelevant information. The command Smartlog will show the drops that are indexed and stored in the SmartEvent database, which may not be in real time and may depend on the log server performance12.
1: https://sc1.checkpoint.com/documents/R81.10/WebAdminGuides/EN/CP_R81.10_AdvancedTechnicalReferenceGuide/html_frameset.htm 2: https://www.checkpoint.com/downloads/training/DOC-Training-Data-Sheet-CCTE-R81.10-V1.0.pdf
The Check Point R81.20 Gaia Administration Guide describes fw ctl zdebug as a key troubleshooting tool for real-time packet analysis, particularly for drops. The CCTE R81.20 course emphasizes using fw ctl zdebug for kernel-level debugging, including monitoring dropped packets.
For precise details, refer to:
Check Point R81.20 Gaia Administration Guide, section on “fw ctl zdebug” (available via Check Point Support Center).
CCTE R81.20 Courseware, which covers advanced troubleshooting techniques for packet drops (available through authorized training partners).
