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
