Stacking Fundamentals; Stacking Capabilities - Avaya 3500 Series Getting Started

Getting started fundamentals
If the stack connection between the two units fails (a stack cable failure, for example), both stand-
alone units retain the IP settings. To detect if the other stack partner is also using the previous stack
IP settings, each device issues an ARP request on the IP address.
Non-EAP clients connected to the device can still authenticate themselves and maintain connectivity
to the network using Stack Forced Mode. Non-EAP clients authenticate by the device with RADIUS,
which is based on the stack IP address. In Stack Forced Mode, the device retains the IP settings of
the stack of two.
The functional unit stays in Stack Forced Mode until either a reboot or it joins a stack.
A settlement timer prevents several stack failures that occur at an interval of a few seconds to lead
to a device entering Stack Forced Mode after it was part of a stack larger than two units. A device
enters Stack Forced Mode if and only if it was part of a stack of two for 30 seconds or longer.

Stacking fundamentals

This section contains information about the stacking features, such as stack capabilities, stacking
functionality delivery, stack configurations, and Auto Unit Replacement.

Stacking capabilities

ERS 3524GT, ERS 3524GT-PWR+, ERS 3526T, ERS 3526T-PWR+, ERS 3549GTS, ERS
3549GTS-PWR+, ERS 3550T, and ERS 3550T-PWR+ units support stacking capability. The two
rear ports on these models can be used in either standalone mode (default) or stacking mode.
• Standalone Mode — In this mode, the switch rear ports function as follows:
- Provides two additional uplinks or connections to servers or power users and supports
regular port configuration parameters such as Spanning Tree, EAP, VLAN Tagging, MLT/
DMLT/VLACP, and port enable/disable
- Provides fixed port speed at 1000 Mbps Full Duplex operation with the insertion of a
supported SFP in the rear ports. Link and traffic indications are provided on the front left of
each switch where the LEDs for the rear ports illustrate "Down / 27" and "Up / 28" for the
ERS 3526T models, "Down / 25" and "Up / 26" on the ERS 3524GT models, "Down / 50" and
"Up / 51" on the ERS 3549GTS models, and "Down / 51" and "Up / 52" on the ERS 3550T
models as shown in the figures that follow.
• Stacking Mode — In this mode, the switch rear ports function as follows:
- Provides resilient stacking of up to eight stackable units when the two rear SFP ports are
configured for "stacking mode" operation
- LEDs on the front panel of the switches indicate "Base Unit" selection and rear stack port
Up/Down connection status.
Getting Started with Avaya ERS 3500 Series
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Comments on this document? infodev@avaya.com
July 2015