Cabletron Systems SEH-24 User Manual

Also see for SEH-22: User guide

INTRODUCTIONPage 1-3You can stack together up to five SEH hubs using Cabletron Systems’external HubSTACK Interconnect cables. If you want to addmanagement to the stack, Cabletron Systems offers the MicroMMACand the SEHI intelligent hubs. You can stack up to four SEHs withone intelligent hub. Stackable configurations let you maintain onlyone IEEE repeater hop while providing up to 130 Ethernet ports.The SEH-22/24 and SEH-32/34 are functionally identical with theexception of the network ports:• SEH-22, 12 RJ45 network ports and one EPIM port.• SEH-24, 24 RJ45 network ports and two EPIM ports.• SEH-32, one 50 pin Champ connector, providing 12 twistedpair segments, and one EPIM port.• SEH-34, two 50 pin Champ connectors, providing 24 twistedpair segments, and two EPIM ports.1.4 SEH FEATURESRepeater FunctionalityThe SEH fully conforms to the IEEE 802.3 Repeater, AUI, and10BASE-T specifications, and provides the flexibility to connectnetworks using IEEE 802.3, Ethernet Version 1 or Version 2equipment. The SEH transmits re-timed data packets, regenerates thepreamble, extends fragments, and arbitrates collisions.The SEH automatically partitions problem segments, and reconnectsrepaired segments to the network. This feature minimizes the impacton network operation by isolating the problem segment. Only deviceson the problem segment are affected. When the problem is solved, theSEH automatically reconnects the isolated segment to the network.Polarity Detection and CorrectionEach twisted pair port on the SEH incorporates a Polarity Detectionand Correction feature that allows the SEH to pass data regardless ofthe polarity of the twisted pair segment’s receive link. We do notrecommend operating in this condition. If you discover this condition,remove the segment from the network and wire it correctly. Thisreduces the potential for problems if equipment changes are made.