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Magnum 700X Mini-Concentrators Installation and User Guide (05/98)
GARRETT
27
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 Hub/Stack) 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 4.2b show the
Figure 4.2a: Internal Packet Forwarded
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 handling of
external packets are shown in figures
Figure 4.2b: Internal Packets Filtered
4.2c and 4.2d respectively. When an
internal packet’s source address is not
already in the address table, it is
written there. This happens when a
node first sends a packet upon bridge
initialization.
Figure 4.2c: External Packet Forwarded
Note, therefore, that the address table automatically learns addresses,
specifically, it learns those connected via the RPMs in the front of the 700X, a number
typically well under the 256 table addresses size.
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”