Cabletron Systems EMME User Manual page 43

CHAPTER 2: NETWORK PLANNING AND CONFIGURATION
Closets A, B, and C each contain an MMAC-FNB with an EMME, MIMs
and RIC MIMs operating on Ethernet channels A, B, and C. Within each
closet, each Ethernet channel is separately repeated, and each is dedicated
to a specific set of network users (for example, Ethernet A is dedicated to
administration, Ethernet B to engineering, and Ethernet C to personnel).
The Star Hub, which is an MMAC-FNB that is configured similarly to the
closet hubs, is the central repeater interconnect for the closets, but does
not constitute a single point of failure.
The EMME in each MMAC-FNB utilizes the 802.1d Spanning Tree
Algorithm. By configuring the Root Path Cost and the Bridge Priority on
the EMME, primary paths from each segment can be bridged to Network
D from each EMME (indicated by the solid line between Ethernet
channel A and the bridge in closet A, Ethernet channel B and the bridge in
closet B, and Ethernet channel C and the bridge in closet C). The dotted
lines between the other Ethernet channels and the bridge show the backup
paths in a standby condition. If any repeater link fails, or if an active
bridge path fails, one or many backup bridge paths could become active,
replacing the failed repeater link or bridge path.
An additional level of redundancy is achieved by using the cable
redundancy algorithm built into Cabletron's EMME. This feature enables
you to configure redundant bridge paths, with one path remaining in
backup, standby mode until the primary path fails.
In the example, Segment D provides a manageable backbone, using a
MiniMMAC. Segment D provides intercommunication for channels A, B,
and C, as well as serving as the network management segment for the
hierarchy. The individual protocol segments are filtered by the EMME
bridge component, so that the only traffic on segment D is minimal inter-
channel communication (i.e., mail). Otherwise, only network
management data is on segment D, out-of-band of the traffic on channels
A, B, and C.
Page 2-12 EMME USER'S GUIDE