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Extreme Networks Technical Brief

About Power Management and

PoE/PoE-plus

The power management for PoE or PoE-plus is applicable

only if there are one or more Summit X460 (PoE-plus),

Summit X450e (PoE), or Summit X250e (PoE) switches

in a stack.

Each Summit X460, Summit X450e or Summit X250e switch

is equipped with its own independent power supply that

provides power for the PoE ports on that switch. Power is

not shared with other switches in the stack. PoE conﬁgura-

tion and status are maintained on the master node. Conﬁgu-

ration information is sent by the master to the hardware on

each PoE capable switch to be controlled by the local PoE

hardware on that switch. Status is gathered on the master

by querying the PoE hardware on each switch. The power

supply for each Summit X450e switch is capable of provid-

ing a full 15.4 watts per PoE port for all 24 ports or 48 ports,

Summit X460 switches are capable of providing full 30 watts

PoE-plus power for up to a total of 760 watts budget when

two AC PoE PSUs are installed.

About Stacking Node Roles,

Redundancy, and Failover

The ExtremeXOS operating system supports control plane

redundancy and hitless failover for stacks. Hitless failover

is supported to the extent that the failing master node and

all of its ports are operationally lost, including the loss of

supplied power on any PoE ports that the node provided,

but all other nodes and their provided ports continue to

operate. After the failover, the backup node becomes the

master node.

At failover time, a new backup node is selected from the

remaining standby nodes that are conﬁgured to be master

capable. All operational databases are then synchronized

from the new master node to the new backup node. Another

hitless failover is possible only after the initial synchroniza-

tion to the new backup node has completed. This can be seen

using the show switch {detail} command on the

master node and noting that the new backup node is In Sync.

When a backup node transitions to the master node role, it

activates the Management IP interface that is common to the

whole stack. If you have correctly conﬁgured an alternate

management IP address, the IP address remains reachable.

When a standby node is acquired by a master node, the

standby node learns the identity of its backup node. The

master node synchronizes a minimal subset of its databases

with the standby nodes.

When a standby node loses contact with both its acquiring

master and backup nodes, it reboots.

A master node that detects the loss of an acquired standby

node indicates that the slot the standby node occupied is

now empty and ﬂushes its dynamic databases of all informa-

tion previously learned about the lost standby node.

A backup node restarts if the backup node has not completed

its initial synchronization with the master node before the

master node is lost. When a backup node transitions to the

master node role and detects that the master node has not

already synchronized a minimal subset of its databases with a

standby node, the standby node is restarted.

Reboot or Failure of a

Non-Master Node

If a backup node fails, a standby node conﬁgured as

master-capable is elected as the new backup. That new

backup node is then synchronized to the databases of the

master node.

For all non-master nodes, a node that reboots or is power

cycled loses all of its connections to all networks for the

duration of the reboot cycle. Any PoE ports that were

providing power prior to the event do not supply power.

When a non-master node fails, the master node marks the

related slot as empty. All other nodes exclude the failed

node from the control path and any customer-conﬁgured

VLANs, trunk group ports, mirroring ports, and so forth.

Conﬁguring a New Stack

Before deploying a new stack, consider the following

guidelines:

• Plan to use the stack as if it were a single multi-slot

switch. You need to decide the number and type of

stackable switches in the stack and how the stack ports

will be connected to the network.

• Physically locate the intended master and backup

nodes adjacent to each other, and plan to directly

connect these nodes to each other so that ExtremeXOS

application synchronization trafﬁc is localized to a

single stack link.

• Use stacking cables to interconnect the stack nodes into

a ring topology (see Figure 3). Only include the nodes

that are intended to be active in the stack. To see the

recommended procedures for installing and intercon-

necting a stack, refer to the hardware documentation.