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GarrettCom DS 880 User Manual

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Magnum DS880 Dual-Speed Stackable Hubs Installation and User Guide (05/01)

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4.0 OPERATION

This chapter describes the function and operation of the Magnum DS880 hubs.

4.1 Dual-Speed

Functionality

The Magnum DS880-A handles the two different traffic domains separately (unless it

is stacked with a DS880-B). The DS880-B provides switched (bridged) connectivity between

the Ethernet (10Mb/s) and Fast Ethernet (100Mb/s) domains. It joins the two network domains

for unified operation, and filters/ forwards packets in both directions to maximize bandwidth

utilization and performance. Magnum DS880s are hardware plug-and-play devices. There is no

software set-up to be done at installation or for maintenance. The functions of the DS880s are

described in this manual.

Each time a packet is received on one domain of the bridge module, the decision is

taken to either to filter or forward the packet. Errored packets are always filtered. For good

packets, the filter and forward decisions are made based on the destination address contained in

each packet. If the destination address is on the same domain from which the packet originated,

then it is filtered and not forwarded to the other domain. If the destination address is not found

to be a match in the address table for the originating domain, then it is forwarded to the other

domain. If it is a new node address coming in which the switch did not previously know about,

it “learns” the new address and puts it in the correct port address table. See “Address Learning”

for more details.

This diagram below shows the filter / forward logic for both domains.

Magnum DS880-B

Figure 4.1 : Filtering vs. Forwarding in Dual Speed 880-B

10 Mb Domain

100 Mb Traffic

100 Mb Domain

10Mb Domain : 10Mb packets ar
forwarded when the destination addres
NOT

e

se is

in the 10Mb domain address table.

100Mb Domain : 100Mb packets are
forwarded when the destination address is
NOT in the 100Mb domain address table.

10Mb Domain : 10Mb packets are
filtered when the destination address is
in the 10Mb domain address table.

100Mb Domain : 100Mb packets are
filtered when the destination address is
in the 100Mb domain address table.

Bridge Module

10 Mb Traffic

10 BUS

100