Specifications

A.12 Dual Ring Configuration Examples
FDDI Configuration Capabilities A–27
A.12.2 Example 2 — Dual Ring Switches Connected to an External Dual
Ring
As shown in Figure A–22, all of the DECswitch 900EF modules (Switches 1 through
3) can connect directly to the dual ring for this dual ring configuration (similar to the
concentrators shown in Example 1).
Switch 3 has its B port assigned to the front panel port connection and the A port
assigned to the backplane port connection.
Switch 2 has its A and B ports assigned to the backplane ports only (the module’s
front panel ports are not active, nor usable).
Switch 1 has its B port assigned to a backplane port and its A port is assigned to the
front panel port.
You can also assign both A and B ports to the front panel ports (the Stump Primary
building block, see Figure A–8), which allows a single DECswitch 900EF or DEC-
concentrator in a DEChub 900 to connect to an external FDDI backbone network.
Figure A–22 Dual Ring Connections for DECswitch 900EF
Figure A–23 shows the Building block representation of the configuration example
described in Figure A–22.
LKG-10086-96F
Front Panel Ports
A
Backplane Ports
B
ABBA
Switch 1 Switch 2 Switch 3