Spanning Tree Protocol Support; Vlan Support - Cabletron Systems SmartSTACK STS16-20RM Installation And User Manual

Spanning Tree Protocol Support

IBM initially supported only source route bridging (SRB) in its bridges, so most
networks were built to use it. The main consideration for SRB implementations in
switches is the spanning tree algorithm for spanning tree explorers (STEs). IBM
originally implemented a form of the Institute of Electrical and Electronics
Engineers (IEEE) spanning tree algorithm. This algorithm, commonly referred to
as the IBM spanning tree, limits the STE frames to one copy per destination ring.
Some SRB implementations have also implemented the IEEE Spanning Tree
Protocol to be compatible with source route transparent bridges. The IEEE
Spanning Tree Protocol is not compatible with the IBM Spanning Tree Protocol.
The switch supports both the IEEE 802.1D and IBM Spanning Tree Protocols.

VLAN Support

The virtual LAN (VLAN) concept creates a virtual switch within a physical switch
or stack of switches. A VLAN consists of CRFs and has its own bridge relay
function attached. Frames are not forwarded across VLANs and ring numbers must
be unique within a VLAN.
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A VLAN consists of a number of ports of a switch or stack of switches
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No frames are forwarded between ports belonging to different VLANs
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Port groups on different VLANs may be assigned the same ring number, but
ring numbers must be unique within the same VLAN
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For each VLAN, the stack can be assigned a separate IP address
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The spanning tree protocol is executed independently within each VLAN.
However, since all BRFs use the same Bridge ID for the spanning tree
algorithm, the spanning tree protocol will not function if ports from different
BRFs within one switch are connected.
A sample VLAN with a STS16-20RM or a STS16-20FRM is shown in Figure 8.
Switch Overview SmartStack STS16-20RM/STS16-20FRM Token Ring Switches, P/N: 9032957-01
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