13 MAC Address Configuration
13.1 Managing the MAC Address
Table
13.1.1 Overview
The MAC address table contains address information used for forwarding packets between
ports. The MAC address table includes three types of addresses: Dynamic address, Static
address, Filtering address. We will describe the MAC address table in the following sections:
13.1.1.1 Dynamic Address
A dynamic address is an MAC address learnt by the device from the packets it receives.
When the device receives a packet on each port, the device will add the source address of
the packet and its associated port number to the address table. The device learns new
addresses in this way.
When the device receives a packet, if the destination MAC address of the packet is the
dynamic address learnt by the device, the packet will be directly forwarded to the port
associated with the MAC address. Otherwise, the packet will be forwarded to all other ports.
The device updates the dynamic address table through learning the new addresses and the
address aged out that are not in use. For an address in the address table, if the device does
not receive any packets with the same source MAC address for a long time (According to the
aging time), the address will be aged. You can adjust the aging time of dynamic address
according to the actual situation. If the aging time is too short, the address in the address
table will be aged too early and the address will be taken as an unknown address again for
the devices. When the device receives the packets with the destination MAC address, the
packets will be broadcast to other ports in the VLAN, leading to the needless broadcast flow .
If the aging time is too long, the address will be aged slowly and the address table will full be
ocupied. When the table is full, no new address can be leant, and all other addresses will
become unknown addresses before there is room for the address table to learn this address.
When the device receives the packets with the destination address, the packet will be
broadcasted to other ports in the VLAN to lead to the needless broadcast being generated..
When the device is reset, all the dynamic addresses that the device have learnt will be lost,
therefore, the device need to learn these addresses again.
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