Specifications

A.12 Dual Ring Configuration Examples
FDDI Configuration Capabilities A–25
A.12 Dual Ring Configuration Examples
Both dual rings and trees are supported across the DEChub 900 MultiSwitch back-
plane. However, because it has more robust and quicker fault tolerance capabilities
than tree configurations, the dual ring configuration is more effective to use across
the backplane.
This section provides four examples of FDDI dual ring configurations that are sup-
ported in the DEChub 900 backplane:
• Example 1 — Dual Ring Concentrators Connected to an External Dual Ring
• Example 2 — Dual Ring Switches Connected to an External Dual Ring
• Example 3 — PEswitch 900TX Connections to an External Dual Ring
• Example 4 — Self Contained Dual Ring in the Backplane
A.12.1 Example 1 — Dual Ring Concentrators Connected to an External
Dual Ring
As shown in Figure A–20, all of the concentrators connect directly to the dual ring
for this dual ring configuration.
Concentrator 3 has one of its front panel ports configured as the external B port con-
nection to the dual ring and one of its backplane ports configured as the A port.
Concentrator 2 uses both backplane ports as the A port and B port connections to the
dual ring.
Concentrator 1 uses the backplane B port connection to the dual ring allowing the
dual ring to exit through a front panel A port.