3Com 3C780 User Guide - Page 80

Attachment, Attachment Ports Configuration

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3-12 Configuring the Hub Table 3-2. Selecting Port Configurations for Attachment Types Attachment Type Attachment Ports Configuration Dual attachment B/A* Dual homing attachment B/A* Single attachment S/M Null attachment M/M *The B/A configuration supports both dual attachment and dual homing. The B and A ports are used to dual attach the hub to the trunk ring or dual home to other hubs. The FDDI connection rules connect the MAC and the attachment ports to the primary ring. The secondary ring is used only to complete the primary ring through the hub and wrap the ring if a fault occurs or a station fails on the primary ring. If you attach the hub in a dual homed configuration, the B port is used as the primary link (B precedence rule), and the A port becomes the backup link. If the primary link fails, the backup link is enabled. To achieve a dual homed configuration, connect the A and B ports to neighbor M ports on one or two other hubs or other devices.

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3-12
Configuring the Hub
Table 3-2.
Selecting Port Configurations for Attachment Types
Attachment
Type
Attachment Ports Configuration
Dual attachment
B/A*
Dual homing attachment
B/A*
Single attachment
S/M
Null attachment
M/M
*The B/A configuration supports both dual attachment and dual homing.
The B and A ports are used to dual attach the hub to the trunk ring or dual home
to other hubs.
The FDDI connection rules connect the MAC and the attachment ports to the
primary ring.
The secondary ring is used only to complete the primary ring
through the hub and wrap the ring if a fault occurs or a station fails on the
primary ring.
If you attach the hub in a dual homed configuration, the B port is used as the
primary link (B precedence rule), and the A port becomes the backup link.
If
the primary link fails, the backup link is enabled.
To achieve a dual homed
configuration, connect the A and B ports to neighbor M ports on one or two
other hubs or other devices.