Nortel Networks 2500 Series manual Redundant cascade stacking

52Nortel Ethernet Routing Switch 2500 Series stacking

This automatic failover is only a temporary safeguard. If the stack configuration loses power, the temporary base unit cannot power up as the base unit when power is restored. Also, if the original unit rejoins the stack, it cannot resume base unit status. For this reason, always assign the temporary base unit as the base unit until the failed unit is repaired or replaced.

ATTENTION

If the temporary base unit is not assigned as the new base unit, and the temporary base unit fails, the next unit in the stack order becomes the temporary base unit. This process continues after successive failures until only two units are left in the stack.

Redundant cascade stacking

The Nortel Ethernet Routing Switch 2500 Series allows a stack of up to 8 units into a dual-path cascade stack. If any single unit fails or if a cable is accidently disconnected, other units in the stack remain operational without interruption.

In addition to increasing bandwidth, the software uses the cables to provide two paths between units. If one path breaks the data travels over the remaining path with half the normal inter-switch bandwidth.

The following diagram shows an example of a stack configuration with a unit failure in the stack. This illustrates:

•Unit 3 becomes non-operational due to a unit failure, cable disconnection, or a loss of power.

•Units 2 and 4, directly upstream and downstream from Unit 3, sense the loss of link signals from unit 3. The software causes all the data to traverse the remaining path.

•The Cascade Down LED for Unit 2 and the Cascade Up LED for Unit 4 turn amber to indicate an error has been detected.

•The remaining stack units continue to be connected.

Nortel Ethernet Routing Switch 2500 Series

Overview — System Configuration

NN47215-500 (323162-B) 02.02 Standard

4.1 19 November 2007

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