Dual Homing; Dual Homing Connections - 3Com 3C780 - LinkBuilder FDDI Base Unit User Manual

3-6 Configuring the Hub

Dual Homing

Dual homing (DH) configuration provides two attachments to the FDDI
network. One of them functions as a backup link if the primary link fails. This
type of attachment is especially useful for connecting to mission-critical
devices.
Figure 3-5 illustrates valid connections for a dual homed hub.
Figure 3-5. Dual Homing Connections
Ports A and B are both connected to the primary ring. Following the B
precedence rule, the B port always takes precedence and becomes the primary
link. If the connection to the B port fails, the A port serves as the backup and
automatically becomes the primary port. The dual homed hub shown in Figure
3-5 is actually a dual attachment hub, but only one port is active at a time.
DAC
Dual
homed
backup
link
A
Server on FDDI
Dual homed hub
Workstation on FDDI
DAC
Primary
link
B
Host on FDDI