Mac Address Learning Mechanism - Huawei Quidway S3100 Series Operation Manual

MAC
Operation Manual –
Quidway S3100 Series Ethernet Switches
Table 1-1 lists the different types of MAC address entries and their characteristics.
Table 1-1 Characteristics of different types of MAC address entries
MAC address entry
Static MAC address
entries
Dynamic
address table
Blackhole
address entry

1.1.3 MAC Address Learning Mechanism

The MAC address learning mechanism enables a switch to acquire the MAC addresses
of the network devices on the segments connected to the ports of the switch. A packet
can be directly forwarded if its destination MAC address is already learnt by the switch.
The MAC address learning mechanism is implemented as follows:
When a switch receives a packet from one of its ports (referred to as Port A), the
switch extracts the source MAC address (referred to as MAC-S) of the packet and
considers that the packets destined for MAC-S can be forwarded through Port A.
If the MAC address table already contains MAC-S, the switch refreshes the aging
time of the corresponding MAC address entry. Otherwise, the switch adds MAC-S
and Port A as a new MAC address entry to the MAC address table.
The switch searches the MAC address table for the destination MAC address of
the received packet. If it finds a match, it directly forwards the packet, or else it
broadcasts the packet in the corresponding VLAN.
When a broadcast packet reaches the network device whose MAC address is the
destination MAC address of the packet, the network device returns a packet to the
switch, with its MAC address contained in the packet.
The switch extracts the MAC address of the network device from the returned
packet and adds a MAC address entry accordingly in its MAC address table. After
that, the switch can directly forward other packets destined for the same network
device by the newly added MAC address entry.
Forwarding Table
Address
Configuration
method
Manually configured
Manually configured
MAC or generated
MAC
learning mechanism
MAC
Manually configured
Huawei Technologies Proprietary
Chapter 1 MAC Address Table Management
Aging time
Unavailable
by
Available
address
Unavailable
1-2
Reserved or not at
reboot (if the
configuration is
saved)
Yes
No
Yes