H3C Technologies H3C WX5500E Series Access Controllers - Manual (Page 33)

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To improve the port security and prevent hackers from stealing data by using forged MAC addresses, you
can bind specific user devices to the port by manually adding MAC address entries to the MAC address
table of the device.
Types of MAC address entries
A MAC address table can contain the following types of entries:
• Static entries—Static entries are manually added in order to forward frames with specific
destination MAC addresses out of their associated ports and never age out.
• Dynamic entries—Dynamic entries can be manually added or dynamically learned in order to
forward frames with specific destination MAC addresses out of their associated ports and might
age out.
• Blackhole entries—Blackhole entries are manually configured and never age out. Blackhole entries
are configured for filtering out frames with specific source or destination MAC addresses. For
example, to block all packets destined for a specific user for security concerns, you can configure
the MAC address of this user as a blackhole MAC address entry.
To adapt to network changes and prevent inactive entries from occupying table space, an aging
mechanism is adopted for dynamic MAC address entries. Each time a dynamic MAC address entry is
learned or created, an aging timer starts. If the entry has not updated when the aging timer expires, the
device deletes the entry. If the entry has updated before the aging timer expires, the aging timer restarts.
A static or blackhole unicast MAC address entry can overwrite a dynamic MAC address entry, but not
vice versa.
MAC address table-based frame forwarding
When forwarding a frame, the device adopts the following forwarding modes based on the MAC
address table:
• Unicast mode—If an entry is available for the destination MAC address, the device forwards the
frame out of the outgoing port indicated by the MAC address entry.
• Broadcast mode—If the device receives a frame with the destination address as all-ones, or no entry
is available for the destination MAC address, the device broadcasts the frame to all interfaces
except the receiving interface.
Configuration procedure
The configuration tasks discussed in the following sections are all optional and can be performed in any
order.
The MAC address table can contain only Layer 2 Ethernet ports and Layer 2 aggregate interfaces.
This document covers the configuration of unicast MAC address entries, including static, dynamic, and
blackhole MAC address entries. For information about configuring static multicast MAC address entries,
see IP Multicast Configuration Guide.