GarrettCom DS 880 - Manual (Page 14)

Magnum DS880 Dual-Speed Stackable Hubs Installation and User Guide (05/01)
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2.4 Bridge Module between the 10Mb and 100Mb Domains
Bridge Module
Figure 2.4 : Internal view of
DS880-B with bridge
module installed
Magnum DS880-B’s contain a factory-installed bridge module to interconnect the two
traffic domains, filtering and selectively forwarding packets to allow only necessary packets to
cross between the domains. This enables all of the users and nodes connected into either
domain, whether 100Mb or 10Mb, to talk to each other, and it keeps local traffic on one domain
from consuming any of the bandwidth of the other domain.
The bridge operates in the store-and-forward mode, which filters out bad packets and
maintains optimum performance in both domains. Packet forwarding delay is only 5
µs (plus
packet time), much less than traditional store-and-forward bridge products, enabling the
DS880s to maintain high network performance. The bridge has 8K node address capacity,
suitable for use in large networks. Addresses are self-learning so that filtering / forwarding of
10Mb and of 100Mb packets is maintained correctly even when users move their connection, or
change speed, or power down.
The DS880-B’s bridge module is implemented as a daughter board. DS880 units have
an LED on the front labeled ‘BR’ that will be ‘ON’ when the module is installed internally.
Power any DS880 unit on and if the BR LED is ON, it is a Magnum DS880-B unit.
NOTE : Only one Magnum DS880-B (with a bridge module built-in) is
allowed per repeater stack. Thus, if the DS880s in a stack have more than one
BR (bridge) LED ‘ON’, it is an illegal configuration.
2.5 Up-link Switch on Port 8 for Cascading
The unit has an up-link switch for Port # 8, located on the right-front side of the hub.
It enables the port’s cable to either connect to a user station ( = position) or to be cascaded to
another hub (X position). (See Section 4.4 for more details about up-link). Like all DS880
ports, Port # 8 is a dual-speed port which will sense the speed of the connected device. The up-
link switch operates the same, whether Port # 8 is connected to either 100Mb or 10Mb devices.
When the up-link port is used to cascade two DS880 hubs or stacks together, the auto-
sensing feature will cause the connecting link to operate at 100Mb speed.