Specifications

Extreme Networks Technical Brief
© 2010 Extreme Networks, Inc. All rights reser ved. SummitStack Stacking Technology—Page 3
Understanding SummitStack
Configuration Parameters,
Configuration Files, and
Port Numbering
Stacking configurations are stored in the NVRAM of each
node. Some of these configurations take effect only during
the next node restart. See Table 2 for stacking configuration
items, times of effect and default values.
Stacking parameters, such as mode, slot number, etc., can
be configured from a single unit in the stack topology. You
can change the stacking-specific configuration even when a
node is not in stacking mode but is connected to the stack.
The target node for the configuration must be powered on
and running a version of ExtremeXOS that supports
stacking. Further, the node need not be in stacking mode
and can be in any node role.
Most ExtremeXOS configuration parameters are not stored
in NVRAM, but are instead stored in a configuration file.
Configurations stored in NVRAM are those that are needed
when the configuration file is not available. The configura-
tion file chosen for the stack is the one selected on the
master node that is first elected after a stack restart.
Stack Depth
A maximum of eight nodes are supported in the active
topology. The slot number configuration assigns only
numbers from one to eight.
The stack tolerates an accidental connection of up to 17
nodes. Because only eight nodes can join an active topology,
there should never be an accidental connection of two
stacks resulting in more than 16 nodes. If you have more
than 17 nodes in a stack topology, all nodes enter an
overflow state and all stacking links enter a link overflow
state. While in an overflow state, the active topology does
not function. All slots containing active nodes show a failed
state. The overflow state is maintained until the overflow is
cleared by manually disconnecting a sufficient number of
nodes. After the overflow is cleared all nodes in the stack
topology reboot.
To see all the nodes in a stack topology, use the show
stacking command.
Configuration Item Takes Effect Default Value
Stacking Mode At boot time Disabled
Slot Number At boot time 1
Master-Capable At boot time Yes
License Registration At boot time Not configured
Priority At the next master election Automatic
Alternate IP Address Immediately Not configured
Stack MAC At boot time Not configured
Table 2: Stacking Configuration Items, Time of Effect
and Default Value
The data (non-stacking) port numbers, in the existing
configuration files (which were created when not in
stacking mode), are simple integer quantities. On a stack,
the data port numbers are expressed as slot:port where the
slot is an integer representing the slot and port is an integer
representing the port, for example: 1:2. The configuration
file contains an indication that it was created on a stackable
switch in stacking mode. The indication is the stacking
platform ID.
Thus when in stacking mode, the ports are referenced in the
configuration file with the slot:port notation and when not in
stacking mode, the ports are referenced as simple integers.
Figure 4: Summit X250e Series in
Daisy-Chain Topology
Daisy-Chain Topology
Stackable switches may be connected in a daisy-chain topol-
ogy. This is a ring topology with one of the links discon-
nected, inoperative, or disabled. A daisy chain can be
created when a link fails or a node reboots in a ring
topology, but the daisy-chain topology is not recommended
for normal operation. In Figure 4, the nodes delineated as
the active topology are operating in a daisy-chain configura-
tion, even though there is physically a ring connection in
the stack.