Cisco ASA Series

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Cisco ASA Series CLI Configuration Guide
Chapter 1 Configuring the Transparent or Routed Firewall
Information About the Firewall Mode
Information About Transparent Firewall Mode
Traditionally, a firewall is a routed hop and acts as a default gateway for hosts that connect to one of its
screened subnets. A transparent firewall, on the other hand, is a Layer 2 firewall that acts like a “bump
in the wire,” or a “stealth firewall,” and is not seen as a router hop to connected devices.
• Using the Transparent Firewall in Your Network, page 1-2
• Bridge Groups, page 1-3
• Management Interface (ASA 5510 and Higher), page 1-4
• Allowing Layer 3 Traffic, page 1-4
• Allowed MAC Addresses, page 1-5
• Passing Traffic Not Allowed in Routed Mode, page 1-5
• BPDU Handling, page 1-5
• MAC Address vs. Route Lookups, page 1-6
• ARP Inspection, page 1-6
• MAC Address Table, page 1-7
Using the Transparent Firewall in Your Network
The ASA connects the same network between its interfaces. Because the firewall is not a routed hop, you
can easily introduce a transparent firewall into an existing network.