Cabletron Systems STS16-20R - Manual (Page 48)

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SmartStack STS16-20D/STS16-20R Token Ring Switches Installation and User Guide Switch Overview
Figure 10. Example of Dynamic Source Route Recovery, Switch 1 Failed
Note that since a separate link is required for forwarding traffic with a given Route
Descriptor, one switch can only carry backup traffic for one failed switch at a time.
This means that a total of 2
×
n switches is required to handle simultaneous failure
of n switches.
While the above example shows redundancy for a BRF with two CRFs, it is also
possible to provide (partial) redundancy for a BRF with more than two CRFs. This
must, however, be accomplished by creating separate DSRR instances for selected
CRF pairs. Note that since at least one of the CRFs must be connected to a legacy
Token-Ring, it is not possible to provide full redundancy for a BRF with more than
one ATM CRF.
Backup BRF
Inactive
Backup BRF
Bridge No. B1
Active
BRF
Bridge No. B1
BRF
Bridge No. B2
A
T
M
A
T
M
A
T
M
A
T
M