IBM 990 - Manual (Page 251)

Appendix A. Hardware Management Console (HMC) 239
Figure A-3 Token ring only wiring scenario
Additional token ring only wiring scenario
Additional connections to the token ring LAN may be made to expand the connectivity beyond
the local Hardware Management Console and Support Elements, as shown in Figure A-4 on
page 240.
If connections to previous generations of Enterprise Server systems are desired, they may be
connected using the MAU in the system, or they may be connected using token ring-to-token
ring bridges.
If connection to the enterprise LAN is desired, it is recommended that a token ring bridge be
installed to isolate the Hardware Management Console and Support Elements from other
systems.
If connection to a central site focal point is desired, a local control unit can be attached to the
LAN.
z990
Primary
SE
Alternate
SE
Token-Ring LAN Token-Ring LAN