Table 15: List of Stacking Terms (continued)
Term
Description
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 master (or
primary), backup, or standby.
Master node
The node that is elected as the master (or primary) node in the stack. The
master 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 master node controls all of its own data ports as well as all data ports
on the backup and standby nodes. To accomplish this, the master 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 master if the master node fails.
The master node keeps the backup node's databases synchronized with
its own databases in preparation for such an event.
If and when the master node fails, the backup node becomes the master
node and begins operating with the databases it has previously received.
In this way, all other nodes in the stack can continue operating.
Standby node
A node that is prepared to become a backup node in the event that the
backup node becomes the master node. When a backup node becomes a
master node, the new master node synchronizes all of its databases to the
new backup node.
When a node operates in a standby role, most databases are not
synchronized – except those few that directly relate to hardware
programming.
Acquired node
A standby or backup node that is acquired by a master node. This means
that the master node has used its databases to program the hardware of
the standby or backup node. The standby or backup node has acted as a
hardware programming proxy, accepting the instructions of the master
node to do so.
An acquired backup node maintains the databases needed to reflect why
the hardware is programmed as it is. However, a standby node does not.
An acquired node can be re-acquired (without a reboot) by the backup
node only when the backup node becomes the master node, and only
when both the backup and standby nodes were already acquired by the
same master node at the time of its failure.
Data ports
The set of ports on a stackable switch that are available for connection to
your data networks. Such ports can be members of a user-configured
VLAN or trunk group. They can be used for Layer 2 and 3 forwarding of
user data traffic, for mirroring, or other features you can configure. Data
ports are different from stacking ports.
Building Stacks
SummitStack Terms
ExtremeSwitching 5420 Series Hardware Installation Guide
59
