Introduction To Transparent Bridge - Huawei AR530 series Configuration Manual

Huawei AR530&AR550 Series Industrial Switch Routers
Configuration Guide - Ethernet Switching

9.1 Introduction to Transparent Bridge

Definition
Transparent bridges are applied in Ethernet environments to connect LANs, to facilitate seamless
interaction between LANs. A transparent bridge learns the network topology needed to forward
packets by reading the received packet's source MAC address and creating a mapping table
between the source MAC address and the interface.
Purpose
Ethernet LAN has become the mainstream technology due to its robust expansibility and low
costs. On some small-scale networks especially on dispersed networks, interworking between
LANs remains a problem and needs to be addressed urgently.
Traditional routers can connect LANs, but the costs are high and the configurations are complex.
Transparent bridging can be used on an Ethernet network to connect LANs.
Transparent bridging makes full use of links but not low-speed Ethernet links to connect LANs
without affecting the existing LAN network. Transparent bridging is easy to use and cost-
effective, so it is widely used.
9.2 Principles
9.2.1 Basic Principles of Transparent Bridging
Forwarding Entry Learning
Transparent bridging uses a forwarding table to forward packets. A network bridge's forwarding
table records the mapping between the MAC address and the packet's outbound interface. If an
Ethernet frame arrives, the network bridge takes the following actions to forward it:
l
l
As shown in
bridge port Port1 and PC2 connects to bridge port Port2. When PC1 sends an Ethernet frame to
PC2, both Port1 and PC2 receive the frame.
Issue 01 (2014-11-30)
Obtain the source MAC address of the valid Ethernet frame.
Add the mapping relationship between the source MAC address and the interface to the
forwarding table to generate a forwarding entry.
Figure 9-1, PC1, PC2, PC3, and PC4 are located on two LANs. PC 1 connects to
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