Customizing The Mac Address Table; Mac Address Table Overview - Cisco Catalyst 6500 Series Configuration Manual

Configuring Bridging Parameters and
ARP Inspection
Transparent firewall mode only
This chapter tells how to customize bridging operations and how to enable ARP inspection for the
transparent firewall. This chapter includes the following sections:
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Customizing the MAC Address Table

This section includes the following topics:
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MAC Address Table Overview

The FWSM learns and builds a MAC address table in a similar way as a normal bridge or switch: when
a device sends a packet through the FWSM, the FWSM adds the MAC address to its table. The table
associates the MAC address with the source interface so that the FWSM knows to send any packets
addressed to the device out the correct interface.
Because the FWSM is a firewall, if the destination MAC address of a packet is not in the table, the
FWSM does not flood the original packet on all interfaces as a normal bridge does. Instead, it generates
the following packets for directly connected devices or for remote devices:
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The original packet is dropped.
OL-6392-01
Customizing the MAC Address Table, page 7-1
Configuring ARP Inspection, page 7-3
MAC Address Table Overview, page 7-1
Adding a Static MAC Address, page 7-2
Setting the MAC Address Timeout, page 7-2
Disabling MAC Address Learning, page 7-2
Viewing the MAC Address Table, page 7-3
Packets for directly connected devices—The FWSM generates an ARP request for the destination
IP address, so that the FWSM can learn which interface receives the ARP response.
Packets for remote devices—The FWSM generates a ping to the destination IP address so that the
FWSM can learn which interface receives the ping reply.
Catalyst 6500 Series Switch and Cisco 7600 Series Router Firewall Services Module Configuration Guide
C H A P T E R
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