SNR S2989G-8TX — настройка динамического обучения MAC-адресов в сетевых устройствах [155/553]

Превью страниц Страница 155 / 553

2-91

S2989G-24TX Operation Manual Chapter 2 Layer 2 services

Configuration

1. Obtain a MAC address.

2. Forward or filter data frame according to the MAC table.

2.21.1.1 Obtaining MAC Table

The MAC table can be built up statically and dynamically. Static configuration is to set

up a mapping between the MAC addresses and the ports; dynamic learning is the process

in which the switch learns the mapping between MAC addresses and ports, and updates

the MAC table regularly. In this section, we will focus on the dynamic learning process of

MAC table.

Figure 2-32 MAC Table dynamic learning

The topology of the figure above: 4 PCs connected to switch, where PC1 and PC2

belongs to a same physical segment (same collision domain), the physical segment

connects to port 1/0/5 of switch; PC3 and PC4 belongs to the same physical segment that

connects to port 1/0/12 of switch.

The initial MAC table contains no address mapping entries. Take the communication

of PC1 and PC3 as an example, the MAC address learning process is as follow:

1. When PC1 sends message to PC3, the switch receives the source MAC address 00-

01-11-11-11-11 from this message, the mapping entry of 00-01-11-11-11-11 and port

1/0/5 is added to the switch MAC table.

2. At the same time, the switch learns the message is destined to 00-01-33-33-33-33, as

the MAC table contains only a mapping entry of MAC address 00-01-11-11-11-11 and

port1/0/5, and no port mapping for 00-01-33-33-33-33 present, the switch broadcast

this message to all the ports in the switch (assuming all ports belong to the default

VLAN1).

3. PC3 and PC4 on port 1/0/12 receive the message sent by PC1, but PC4 will not reply,