Cabletron Systems SmartSTACK ELS10-27TX Supplement Manual

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Configuring Workgroups Using LCM5-3It is also possible to overlap workgroups. Figure 5-2 shows how overlappingports can communicate with ports in both Workgroups. For example, WorkgroupAlpha 3-7 and Workgroup Omega 7-9. In this example, four workgroups wouldbe created, Alpha, Omega, the default, and a superset workgroup containing allports in Alpha and Omega. In this case ports 3-6 would be limited tocommunicating with ports within Alpha. Ports 8 and 9 would be limited tocommunicating with ports in Omega. However, port 7 can communicate withports within both Alpha and Omega.Figure 5-2. Traffic Overlapping Within WorkgroupsThe system is able to do this because the system places additional entries in thedatabase that allow the two-way communication. In the previous example, whena packet is received on port 7, its source MAC address is stored in the databasewith a Workgroup identifier. In this case it is the identifier of the superset(0x06e). When a device on ports 3-6 or 8 and 9 try to send a packet to that MACaddress, it has no way of combining the destination MAC address with theWorkgroup identifier for port 7 (0x06e). For example, if the packet is received onport 3, the packet is labeled with the Workgroup identifier for Workgroup Alpha(0x065). A lookup will be done on the MAC address and Workgroup ID pair(0x065). In this case, it would not be found and the packet would be flooded toall members of Workgroup Alpha. The two devices would be able tocommunicate, but only because of the flooding.To avoid flooding, the system places additional entries into the database. Whenthe first packet is received on port 7, three entries are placed into the database.One for the superset (0x06e), one for Alpha (0x065), and one for Omega(0x066). By placing three entries, when the responding device sends a packet toPorts 3, 4, 5, 6, 7 Ports 3 through 9Workgroup Superset Workgroup OmegaWorkgroup AlphaPorts 1, 2, and 10 through 27Workgroup Default7 8, 9