3Com WX3000 operation manual MAC Address Table Management, Introduction to MAC Address Table

1 MAC Address Table Management

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The term switch used throughout this chapter refers to a switching device in a generic sense or the switching engine of a unified switch in the WX3000 series.

The sample output information in this manual was created on the WX3024. The output information on your device may vary.

This chapter describes the management of static, dynamic, and blackhole MAC address entries. For information about the management of multicast MAC address entries, refer to the part related to multicast protocol.

Overview

Introduction to MAC Address Table

A switch is mainly used to forward packets at the data link layer, that is, transmit the packets to the corresponding ports according to the destination MAC address of the packets. To forward packets quickly, a switch maintains a MAC address table, which is a Layer 2 address table recording the MAC address-to-forwarding port association. Each entry in a MAC address table contains the following fields:

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Destination MAC address

ID of the VLAN which a port belongs to

Forwarding egress port numbers on the local switch

When forwarding a packet, a switch adopts one of the two forwarding methods based on the MAC address table entries.

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Unicast forwarding: If the destination MAC address carried in the packet is included in a MAC address table entry, the device forwards the packet through the forwarding egress port in the entry. Broadcast forwarding: If the destination MAC address carried in the packet is not included in the MAC address table, the device broadcasts the packet to all ports except the one receiving the packet.

Introduction to MAC Address Learning

MAC address table entries can be updated and maintained through the following two ways:

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Manual configuration MAC address learning

Generally, the majority of MAC address entries are created and maintained through MAC address learning. The following describes the MAC address learning process of the device:

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