Allied Telesyn International Corp TurboStack AT-S6 User's Guide download pdf (Page 59)

Chapter 4

Fault Tolerance

This chapter describes the behavior of master and slave hubs in terms of

module failure in a chassis conﬁguration. It also provides procedures on

how to swap failed modules in the chassis.

CAUTION

NEVER power off modules while they are in the chassis, because modules

are not isolated from the backplane. When power cycling, ALWAYS slide

the module out first, disconnect the power cord, reconnect the power cord,

and then slide the module back in.

As mentioned in Chapter 1, you can stack multiple TurboStack hubs in

the same chassis with backplane and manage them via the master

module. In a standard conﬁguration, up to eight hubs can all operate

together as one logical concentrator; they share 10 Mbps bandwidth. In a

chassis with segmented backplane conﬁguration (7-slot with internal

switch or 8-slot with external switch), hub modules are each allocated 10

Mbps of bandwidth.

The master is deﬁned to be the module in the lowest numbered

(physically the topmost) occupied slot position. Typically this is slot 1, but

it could be slot 2 if slot 1 is vacant. The other modules in the same

backplane are called slaves. The master manages the modules in the

chassis. With Omega, you can also use the master to conﬁgure and

manage the switch. SNMP, however, treats each module as a independent

units.

The ﬁrst slave in the hub watches over the master and can take over a

failed master’s functions if that ﬁrst slave has management capabilities.

This special module is called the backup. This module is deﬁned as the

one occupying the next higher numbered slot position after the master.

Use only TurboStack hubs with management capabilities as both master

and backup modules.

As described in Chapter 1, a TurboStack hub running ﬁrmware AT-S10

cannot manage AT-3600 hubs. Refer to the section on AT-S10 and AT-S4

interoperability for details.

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Allied Telesyn International Corp TurboStack AT-S6 User's Guide Page 59