Extended Edge Switching on Stacking Overview

With Extended Edge Switching on Stacking, Extended Edge uses the stack, rather than MLAG, to provide redundancy to a BPE. This is done by having certain components of EXOS synchronize their primary and backup nodes with respect to the Extended Edge Switching state. The primary node performs all Extended Edge Switching controlling bridge functions while the backup is kept in sync with the primary. This simplifies configuration, as all stack switches are managed with a single configuration file and control point that resides on the elected primary switch. The backup switch can become the primary switch upon failure of the primary switch if the failure is caused by a crash, a power-off, or a management action.

Use of MLAG in Extended Edge Switching on Stacking

When Stacking provides the controlling bridge, MLAGs will not service individual BPEs. All BPE LAGs that connect to a controlling bridge provided by a stack terminate in a single LAG at the controlling bridge. The LAG at the controlling bridge can consist of member ports provided by different nodes in the stack. Preventing Extended Edge Switching MLAG in Stacking is enforced by the CLI, and ZTPStack will not attempt to activate MLAG on the stack.

MLAG can be used to provide redundancy using two stacks. An MLAG is defined for a user device using stack node front panel ports that are not used to provide the cascade port function.


BPE ports cannot be used to form MLAGs.

Extended Edge Switching and Stack Modes Combined

Either Extended Edge Switching mode or stacking mode can be used independently. A switch reboot is required to enter the combined mode and enable Extended Edge when already in stacking mode. A reboot is also required to enable stacking mode when in Extended Edge Switching mode (assuming that Extended Edge Switching MLAG is not in use). Both can be enabled simultaneously with a single reboot.

Extended Edge Switching Autoconfiguration and ZTPStack

ZTPStack enables both Extended Edge Switching and stacking when bringing up a stack that has attached BPEs. Once in stacking mode and Extended Edge Switching mode simultaneously, ZTPStack (on stacks that have a default EXOS configuration) enables Extended Edge autoconfiguration.

Supported Topologies

BPEs at the “first tier” (directly connected to the stack) can connect any or all of their intended upstream ports to any switch in the stack.

A cascaded BPE (tier 2 or higher) can connect its upstream ports only to the same BPE, meaning only point-to-point upstream topologies are supported below tier 1. Cascade ports that are configured on LAGs impose the restriction that all of the LAG members must be provided by the same BPE, or must all be provided by the stack directly.

Two BPE cascades can be connected together at their ends forming an Extended Edge Switching Ring.

Redudancy and Hitless Failover

Extended Edge Switching on Stacking uses the stack redundancy feature. All of the data and states associated with the Extended Edge Switching feature are continuously checkpointed to the backup node. The backup node is prepared to take over the controlling bridge function for the stack if there is a primary node failure.


All nodes in a stack running Extended Edge Switching must be controlling bridge capable. Any attempt to add a non-capable slot to a stack running Extended Edge will fail. Enabling Extended Edge Switching on a stack that contains a non-capable node will fail.

You must use the same class of controlling bridge for both the primary and backup. For example, if a 5520 series switch is the primary node, then the backup must also be a 5520 series switch.

The primary-capable node in a stack that has the least maximum supported number of BPEs determines the maximum for the stack. When using Extended Edge with Stacking, BPEs cannot be attached to configured MLAG ports.

Supported Platforms

The following devices are supported as controlling bridges (CBs):

ExtremeSwitching 5420 and 5520 series switches.

The V300 and V400 BPEs can be attached to a stack that is configured as a controlling bridge.



The V300-8P-2T-W BPE requires PoE.

Supported Commands

Existing Extended Edge display commands show the same result on the primary and backup nodes.

The enable/disable vpex and enable/disable stacking commands are aware of the capability of each node in the stack. The enable vpex command will fail if any node in the stack is not Extended Edge-capable.

The show slot command shows the Failed state for the attempted addition of a new stack node that does not support the controlling bridge function when the Extended Edge Switching feature is enabled. A message is logged at the time this failure occurs. The show slot command also shows the presence of any BPEs that have occupied slots.

Use the show vpex stacking command to show Extended Edge Switching information for all nodes in the stack topology.