1.1 Introduction to the MAC Address
This section describes the concept of the MAC address.
A Media Access Control (MAC) address defines the location of a network device. A MAC
address consists of 48 bits and is displayed as a 12-digit hexadecimal number. Bits 0 to 23 are
assigned by the IETF and other institutions to identify vendors, and bits 24 to 47 are the unique
ID assigned by vendors to identify their network adapters.
MAC addresses fall into the following types:
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Physical MAC address: uniquely identifies a terminal on an Ethernet network and is the
globally unique hardware address.
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Broadcast MAC address: indicates all terminals on a LAN. The broadcast address is all 1s
(FF-FF-FF-FF-FF-FF).
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Multicast MAC address: indicates a group of terminals on a LAN. All the MAC addresses
with the eighth bit as 1 are multicast MAC addresses (for example, 01-00-00-00-00-00),
excluding the broadcast MAC address.
1.2 Principles
This section describes principles of MAC address table.
1.2.1 MAC Address Table
Each device maintains a MAC address table. A MAC address table records the MAC address,
VLAN ID and outbound interfaces learned from other devices. When forwarding a data frame,
the device searches the MAC table for the outbound interface according to the destination MAC
address and VLAN ID in the frame. This helps the device reduce broadcasting.
Packet Forwarding Based on the MAC Address Table
The device forwards packets based on the MAC address table in either of the following modes:
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Unicast mode: If the destination MAC address of a packet can be found in the MAC address
table, the device forwards the packet through the outbound interface specified in the
matching entry.
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Broadcast mode: If a packet is a broadcast or multicast packet or its destination MAC
address cannot be found in the MAC address table, the device broadcasts the packet to all
the interfaces in the VLAN except the inbound interface.
Categories of MAC Address Entries
The MAC address entry can be classified into the dynamic entry, the static entry and the
blackhole entry.
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The dynamic entry is created by learning the source MAC address. It has aging time.
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The static entry is set by users and is delivered to each SIC. It does not age.
Huawei AR530&AR550 Series Industrial Switch Routers
Configuration Guide - Ethernet Switching
1 MAC Address Table Configuration
Issue 01 (2014-11-30)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
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