GarrettCom 1008 - Manual (Page 36)

Magnum 1000 Workgroup Hubs Installation and User Guide (04/02)
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4.2 Magnum 1000’s with BPM Local Bridge Functionality
When configured with a BPM, a Magnum 1000 Workgroup Hub and its
attached devices are bridge-isolated from the network segment connected through the
BPM. The bridge functionality of the BPM bridge modules is described here.
1. Bridge Functions: Each BPM card contains a compact local bridge
module which filters and forwards packets at full Ethernet wire speed. These
micro-bridges are self learning and have small (256 user) address tables.
Packet filter/forward decisions are made based on whether the
packet source is internal (originates within the local Magnum 1000) or
external (originates from upstream
on the attached segment). If the
packet’s source is internal, it is
forwarded to the outside only if the
destination address is not in the
address table. Figure 4.2a shows
an internal packet being forwarded
to the external segment. Figure 4.2a: Internal
Packet Forwarded
Figure 4.2b show the
cases where an internal packet is
filtered. When the packet’s
source is external, it is forwarded
to the inside only if the
destination address is in the
address table.
The filter/forward Figure 4.2b: Internal Packet Filtered
handling of external packets
are shown in figures 4.2c and
4.2d respectively. When an
internal packet’s source
address is not already in the
address table, it is written
Internal packets
are forwarded when
the destination is
NOT IN the address
table.
FWD-X LED “ON”
Internal packets
are filtered when
the destination is
IN the address
table.
External packets
are forwarded when
the destination is
IN the address
table.
FWD-I LED “ON”