GE T1000, Техническое руководство

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Chapter 4
– Functions
GE Reason Switches
76 REASON SWITCHES-TM-EN-3
8 MAC Table
Ethernet switches operate in a context of transparent bridge packet switching, which
is a fundamental concept in Ethernet packet switching. There are some topics, thus,
that must be matched by Ethernet switches, which are

Each station (host) attached to a transparent bridge has a globally unique
address (MAC address);

A bridge has an interface connected to all LANs that the bridge belongs to;

The bridge has information to reach all stations that it is connected to;

A bridge operates in promiscuous mode, in which it receives all frames at all
interfaces, regardless the destination address;
There are some additional features that a switch must perform, such as:

Packet filtering;
o
If the source MAC address of a given packet is attached at the
interface where it was received, the packet will be discarded by the
switch.

Multicast forwarding
o
A multicast addressed frame must be forwarded to all interfaces
except the incoming frame interface
If one of these concepts is violated, the network would not work properly.
Reason Switches, by default, are set to operate as a transparent bridge, i.e., as a common switch.
An example of the Ethernet frame is shown in Figure 35 below.
Figure 37: Ethernet frame
As can be seen, the destination and source addresses are attached directly at the
Ethernet frame. Thus, a switch must be able at least to handle these fields to perform
its main function, being a transparent bridge in a packet-switching network
environment.
If a host needs to send data to another host in a switched LAN, it will forward traffic
from its own NIC (Network Interface Card) to the interface that it is connected at the
switch. Then, the switch will map the incoming MAC address in a table, mapping to
an interface. Continuing this process, the switch will map all hosts to reach all
stations connected to it. Note that, for this operation, it is assumed that there is no