Table 8: List of Stacking Terms (continued)
Term
Description
Stack topology
A contiguously connected set of nodes in a stack that are currently
communicating with one another. All nodes that appear in the
show
stacking
command display are present in the stack topology.
Stack path
A data path that is formed over the stacking links for the purpose of
determining the set of nodes that are present in the stack topology and
their locations in the stack. Every node is always present in a stack path
whether or not stacking is enabled on the node.
Control path
A data path that is formed over the stacking links that is dedicated to
carrying control traffic, such as commands to program hardware or
software image data for software upgrade. A node must join the control
path to fully operate in the stack. A node that is disabled for stacking does
not join the control path, but does communicate over the stack path.
Active node
A node that has joined the control path. The active node can forward the
control path messages or can process them. It can also forward data
traffic. Only an active node can appear as a card inserted into a slot when
the
show slot {
slot
{
detail
} |
detail
}
command is
executed on the primary node of the stack.
Active topology
A contiguous set of active nodes in a stack topology plus the set of
stacking links that connect them. When an active topology consists of
more than one node, each node in the active topology is directly and
physically connected to at least one other node in the active topology.
Thus, the active topology is a set of physically contiguous active nodes
within a stack topology.
Candidate node
A node that is a potential member of an active topology, or an active node
that is already a member of an active topology. A candidate node may or
may not be an active mode – that is, it may or may not have joined the
control path.
Node role
The role that each active node plays in the stack – either primary, backup,
or standby.
Primary node
The node that is elected as the primary node in the stack. The primary
node runs all of the configured control protocols such as OSPF (Open
Shortest Path First), RIP (Routing Information Protocol), Spanning Tree,
and EAPS (Extreme Automatic Protection Switching).
The primary node controls all of its own data ports as well as all data ports
on the backup and standby nodes. To accomplish this, the primary node
issues specific programming commands over the control path to the
backup and standby nodes.
Backup node
The node assigned to take over the role of primary if the primary node
fails. The primary node keeps the backup node's databases synchronized
with its own databases in preparation for such an event.
If and when the primary node fails, the backup node becomes the primary
node and begins operating with the databases it has previously received.
In this way, all other nodes in the stack can continue operating.
SummitStack Terms
Build Stacks
42
ExtremeSwitching 5320 Series Hardware Installation Guide
