Transparent Cisco IOS Firewall
The transparent firewall works on Layer 2 information, not Layer 3 of the OSI model. From version 12.3(8) T, IOS Firewall is designed to simultaneously interoperate in both Layer 2 and Layer 3 modes.
You can configure a transparent firewall just like the current L3 firewall using the ip inspect command. The inspect in/out command can be configured on any of the bridged interfaces for Layer 2 protection while also being configured on any LAN or serial interfaces to provide traditional Layer 3 protection. The transparent firewall operates on the bridged packets, and the Layer 3 firewall continues to operate on the routed packets.
To understand the CBAC fully, you must be knowledgeable about all the commands and tools available to troubleshoot the CBAC issues. The section that follows leads you through a discussion of the tools and commands available to troubleshoot CBAC effectively and efficiently.