Slot Numbers; About Redundancy - Extreme Networks Summit X150 Series Hardware Installation Manual

Building a SummitStack Configuration
all the software tables for all the switches in the stack. A stack of switches can have only one master
switch. All switches in the stack, including the master switch, are called nodes.

Slot Numbers

A stack can be thought of as a virtual chassis. Each node operates as if it were occupying a slot in a
chassis and is controlled by the master. The high-speed stacking links function like the backplane links
of a chassis.
Each switch (or node) in the stack is assigned a "slot number" during the initial software configuration
of the stack. Starting at the switch with the console connection, numbers are assigned in numerical
order following the physical path of the connected stacking cables. For example, if you follow the
cabling recommendations presented in "Connecting the Switches to Form the Stack Ring" on page 101
and configure a vertical stack from the console on the switch at the top of the physical stack, the
switches Figure 71 will be assigned numbers 1 through 8 from the top down.
Each Summit switch has a seven-segment LED on its front panel, called the stack number indicator.
When a stack is operating, the indicator displays the slot number for the switch. This LED does not
light on switches that are not operating in stacking mode. A quick way to verify that the cable
connections match the software configuration is to check the stack number indicator on each switch. If
the slot numbers do not line up in the order you arranged the switches, this may indicate that the
stacking cable setup differs from what you intended when you configured the software. In this case,
reconnect the cables in the correct order and perform the software configuration again.

About Redundancy

When your stack is operational, one switch is the primary (or master) switch that is responsible for
running network protocols and managing the stack. To provide recovery in case of a break in the stack
connections, you can configure redundancy by designating a backup switch to take over as master if the
master switch fails. When you perform the initial software configuration of the stack, the "easy setup"
configuration option automatically configures redundancy, with slot 1 as the master and slot 2 as the
backup. You can also configure additional switches as "master-capable" to become a stack master in
case the initial backup switch fails.
In a stack that combines Summit X480 series or X650 series switches with other Summit switch models,
a Summit X480 or X650 series switch might provide more memory and more features than other
Summit switch models in the stack. These differences can affect master node selection, backup node
selection, and failover operation. The master and backup roles should be assigned to switches from the
same series. For example, if the master node is a Summit X480 series switch, the backup node should
also be a Summit X480 switch. Similarly, if the master node is a Summit X650 series switch, the backup
node should also be a Summit X650 switch.
In a stack that combines Summit X480 series switches with Summit X650 series switches, Extreme
Networks recommends assigning the master/backup roles to two Summit X480 series switches.
In a stack with multiple master-capable switches, it is possible for more than one switch to try become
the stack master if the stack is physically severed. Such a dual-master condition would cause confusion
and loss of connectivity in your network. To resolve a dual-master condition, you must be able to log in
to each severed stack segment, either over the management network (using the Ethernet management
port on a switch in the segment) or through a direct console port connection to each switch in the
segment.
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Summit Family Switches Hardware Installation Guide