Cabletron Systems STS16-20D, STS16-20R manual Source Route Switching SRS, Source Route Bridging SRB

22

The CRF communicates via a logical, virtual port with the bridge relay function, which functions as a multiport (virtual) bridge between the logical rings. The SmartStack STS16-20D/STS16-20R can support up to 63 logical rings.

There are two levels of relay functions supported by the SmartStack STS16-20D/ STS16-20R. The first level is the CRF to which the ports are assigned. The second level is the BRF. This is the parent relay function to which CRFs are assigned. The SmartStack STS16-20D/STS16-20R maintains certain configuration information and management statistics on a per BRF/CRF basis. Therefore, when you access VLAN-specific SmartStack STS16-20D/STS16-20R configuration or management screens (such as the Current Spanning Tree Information screen), you will be prompted to specify the desired BRF or CRF.

Source Route Switching (SRS)

This mode is used between ports comprising a logical ring.

SRS switching combines the normal transparent bridge function with the ability to forward frames based on source route information to locally attached source-route bridges. The switch does not otherwise act as a source route bridge. For non source- routed packets, the switch decision is based upon destination MAC Addresses. For source-routed packets, it is based on the source-route information combined with the destination MAC address.

The switch learns MAC addresses and source-routing route descriptors of source route bridges attached to local switch ports.

Parallel paths are eliminated via the IEEE 802.1D Spanning Tree Protocol. Note that on SmartStack STS16-20D the spanning tree protocol is only available on the network ports 17 to 20.

➽Note: On SmartStack STS16-20D only the designated network ports 17 to 20 will allow multiple MAC addresses to be learned. On SmartStack STS16-20R all ports allow multiple MAC addresses.

Source Route Bridging (SRB)

The BRF acts as a multiport source route bridge between CRFs with the following characteristics:

•

•

Each logical ring has a different ring number

Source route frames are forwarded between the logical rings by the bridge relay function based on the route information field

•Non-source-routed frames are not forwarded between logical rings

SmartStack STS16-20D/STS16-20R Token Ring Switches Installation and User Guide Switch Overview