Cabletron Systems 24 User Manual

Related ManualsPage 1-5By default, each of the STH hub’s TCU ports is configured to its STN(station) setting to support concentrator lobe connections to stations.Through Local Management, any TCU port may be reconfigured to itsRO (Ring Out) setting to support connections to passive MAU (Multi-Station Access Unit) workgroups.Improved Protection from BeaconingThe STH provides enhanced reliability for existing networks which usepassive MAUs because Multiple Ring Out TCUs allow for the separateattachment of each MAU. Rather than daisy-chaining MAUs together as asingle entity and risking their collective isolation in case of beaconing, theuser can now attach each MAU individually, reducing the number ofMAU ports that are at risk of collective isolation in case of beaconing onthe ring; ABRP is able to bypass individually connected MAUs on anindividual rather than collective basis. See Figure 1-2.No Connection RedundancyThe STH hub’s Ring Out TCU configuration does not provide for theMAU’s redundant connection to the ring. In the common configuration, aMAU chain is dual-attached to the Token Ring LAN via both a Ring Outcable and a Ring In cable. Using a TCU port, however, each passive MAUworkgroup is physically connected to the hub in the same manner as astation—by a single cable—and therefore is not provided a backup pathbetween the MAU and the Token Ring network. Only the dualattachment of Ring In and Ring Out cables can provide a backup path.This level of connectivity must be provided by a dedicated pair of Ring In/ Ring Out ports such as those available on the intelligent hub.1.3 Related ManualsUse the STHi User’s Guide (PN 9031390) and the MicroMMAC-xxTUser’s Guide (PN 9031320) to supplement the procedures and othertechnical data provided in this manual.