SummitStack Technical Brief - Extreme Networks

Extreme Networks Technical Brief: SummitStack, Extreme Networks Virtual Chassis Stacking Technology 

SummitStack, 

Extreme Networks 

Virtual Chassis 

Stacking Technology 

Overview 

Extreme Networks® offers a high-performance 

SummitStack solution that allows up to eight Summit 

switches to join a “virtual chassis.” There are exclusive 

cable-based forms of SummitStack as well as standard 

Ethernet-based versions of the technology. All forms of 

SummitStack allow multiple switches to be managed 

via a single IP address, which reduces complexity 

and makes management easier. As a true stacking 

technology, SummitStack allows switches in the stack 

to behave as a single virtual chassis with a distributed 

forwarding dataplane, rather than a set of individual 

switches managed through a single IP address. 

Extreme Networks SummitStack stacking technology 

enables the physical connection of up to eight 

individual Summit® switches together as a single 

logical unit. This logical unit reduces the management 

overhead of fixed configuration switches by behaving 

as a single switch with a single IP address and a 

single point of authentication. In ExtremeXOS®, 

Extreme Networks edge-to-core modular operating 

system, a stack is controlled by a master switch, 

called the master. The master switch is responsible 

for maintaining all of the software tables for all the 

switches in the stack. There can only be one master 

switch in a stack of switches. All switches in the stack, 

including the master switch, are called nodes. 

SummitStack Basics 

• Stack up to 8 Switches 

• 20-256Gbps Link 

• Virtual Chassis Architecture 

• High availability/Sub 50msec failover 

© 2012 Extreme Networks, Inc. All rights reserved. 

A stack of Summit switches can be thought of as a 

Virtual Chassis. Each node acts as if it was occupying 

a slot in a chassis and is controlled by the master. The 

high-speed stacking links function like the backplane 

links of a chassis. Stacking offers customers a flexible 

way to increase switch density and capacity, provides 

port configuration choices, and controls upfront 

capital requirements. SummitStack permits mixing and 

matching Summit switches in a multi-platform stack 

to provide flexible connection options, from Ethernet, 

Fast Ethernet, Gigabit Ethernet to 10 Gigabit Ethernet, 

in copper, Power over Ethernet (PoE), Power over 

Ethernet Plus (PoE-plus) and fiber optic interfaces. 

SummitStack Advantages 

• Centralized Management 

• Low Connectivity Cost 

• Growth for Future 

• Mix and Match (Cross-platform) 

• Distributed Forwarding 

The master switch stores any configuration information 

for the stack in its primary and secondary flash 

memory. Since the master switch has the knowledge of 

the state and the configuration of all the other switches 

in the stack, it can respond to all external requests for 

those switches. For example, the master switch can 

respond to a request for SNMP information from all 

ports within the stack. 

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SummitStack is supported through dedicated stacking 

port functionality with specific stack cables or through 

the use of existing 10 Gigabit or 40 Gigabit Ethernet 

ports to stack the switches together. The latter option 

allows for physical flexibility when stacking needs to be 

carried over longer distances than is supported in the 

dedicated stacking cables. SummitStack is an Extreme 

Networks solution for fixed configuration switches 

to provide simplified yet agile operations for scalable 

converged networks and data centers. 

Extreme Networks Stacking technology 

come in two basic types, SummitStack, 

leveraging proprietary cables 

and SummitStack-V, leveraging 

conventional Ethernet 

SummitStack Varieties 

Extreme Networks SummitStack is highly versatile. 

In addition to high-performance connectivity 

with proprietary stacking cables (SummitStack, 

SummitStack 128, SummitStack 256 and SummitStack 

512), Extreme Networks also increases range and 

flexibility by offering stacking with conventional 

Ethernet connectors and optics (SummitStack-V, 

SummitStack-V80, SummitStack-V160 and 

SummitStack-V320). The following table summarizes 

the stacking options available on Extreme Networks 

stackable switches. 

Stacking Type Performance per Link Cable Type & Lengths Supported Switch Types 

SummitStack-V - Stacking 

using standardized media 

interfaces such as XFP, 

XENPAK, and SFP+ 

SummitStack - Original 

stacking technology with 

proprietary stacking cables 

SummitStack-V80 - High 

Performance stacking 

utilizing QSFP+ technology 

SummitStack-V160- High 



SummitStack-V320- High 



* Future Availability 


10Gbits/sec 0.5m – 100m SFP+, XFP, 

XENPAK,10GBaseT, LR 

Optics, 40km reach* 

10Gbits/sec 20G Stacking Cable 0.5m, 

1.5m, 3.0m, 5.0m 

Summit X450a, X450e, 

X440-10G, X460, X480, 

X650, X670, X670V 

Summit X250e, X450e, 

X440, X450a, X460, 

X480, X650 (except 5m) 

20Gbits/sec QSFP+ only 0.5-100m Summit X460, X480 

40Gbits/sec QSFP+ only 0.5-100m Summit X480, X650, 

X670V 

80Gbits/sec QSFP+ only 0.5-100m Summit X480, X650, 

X670V 

2


Stacking Type Performance per Link Cable Type & Lengths Supported Switch Types 

SummitStack-128 - High 


technology using 










Table 1: Stacking Options Available on Extreme Networks Stackable Switches 

Stack 

with 

Summit 

X250e 

Summit 

X450e 

Summit 

X440 

Summit 

X440-10G 

Summit 

X450a 

Summit 

X460 

Summit 

X480 

Summit 

X650 

Summit 

X670 

Summit 

X670V 

Summit 

X250e 

Summit 

X450e 


32Gbits/sec 0.5m, 1.0m, 3.0m Summit X480 w/ 

conversion cable to 

SummitStack 256 or 

SummitStack 

64Gbits/sec 0.5m, 1.0m, 3.0m Summit X650 

128Gbits/sec 0.5m, 1.0m, 3.0m Summit X650 

Summit 

X440 

Summit 

X440- 

10G 

Summit 

X450a 

Summit 

X460 

Summit 

X480 

Summit 

X650 

Summit 

X670 

40G 40G 40G - 40G 40G 40G 40G - - 

40G 40G, V 40G V 40G, V 40G, V 40G, V 40G, V V V 

40G 40G 40G - 40G 40G 40G 40G - - 

- V - V V V V V V V 

40G 40G, V 40G V 40G, V 40G, V 40G, V 40G, V V V 

40G 40G, V 40G V 40G, V 40G, V, 

V80 

40G 40G, V 40G V 40G, V 40G, V, 

V80 

40G 40G, V 40G V 40G, V 40G, V, 

V80 

40G, V, 

V80 

40G, V, 

V80, 128G, 

V160, V320 

40G, V, 

V80, 128G, 

V160, V320 

Summit 

X670V 

40G, V, V80 V V, V80 

40G, V, 

V80, 128G, 

V160, V320 

40G, V, 

V160, V320, 

256G, 512G 

V V, V80, 

V160, 

V320 

V V, V160, 

V320 

- V - V V V V V V V 

- V - V V V, V80 V, V80 V, V160, 

V320 

Table 2: SummitStack Stacking Matrix 

V V, V160, 

V320 

3


True Stacking vs. Single IP Management 

“Stacking” is sometimes used to describe the 

ability to manage multiple switches via a single IP 

address. This single IP management can simplify 

management via consolidation, allowing a number 

of devices to be managed via a single representative 

switch. This feature helps IP administrators reduce 

complexity. Although this capability allows having 

one management instance, typically single IP 

management would not provide a method to configure 

data forwarding-related parameters across multiple 

switches simultaneously. For example, if you would 

like to configure VLANs that span multiple switches 

in the same management domain, you would need to 

configure them one-by-one, a time consuming task. For 

single IP management, the connectivity is typically via 

regular Ethernet technologies, such as Fast Ethernet, 

Gigabit Ethernet and 10 Gigabit Ethernet, hence the 

network connectivity and redundancy are based on the 

IEEE 802.1D Ethernet MAC bridging standard, which 

includes bridging and spanning tree protocol. 


True Stacking 

“True stacking” provides the capability for multiple 

stackable switches to behave as one Virtual Chassis. 

With true stacking technology, IT administrators 

benefit from consolidating the management instances 

for, typically, up to eight Ethernet switches, and also 

benefit from consolidating the switch forwarding 

data plane so that the stacked system behaves with 

the simplicity of a modular chassis system. Using true 

stacking, the switching system, including switching 

fabric, is consolidated so that all resources are centrally 

manageable. IT administrators may create VLANs, 

Link Aggregation Groups (LAGs), Access Control 

Lists (ACLs), plus port mirroring across ports in 

different switches within a stack. For true stacking, 

the connectivity is typically via specialized high-speed 

interfaces rather than standard Ethernet links. This 

allows the use of non-Ethernet-based protocols to 

provide multi-path connectivity and redundancy 

within a stack. Unlike other stacking solutions, 

SummitStack provides distributed forwarding which 

enable each switch within the virtual chassis to 

perform “local switching.” 

The table below summarizes the comparison between single IP management and true stacking. 

Attribute Single IP Management True Stacking 

One Management IP Address YES YES 

VLAN Configuration Within a single switch Across all switches in stack 

Switch Forwarding Typically Layer-2 Switching Only Layer-2 or Layer-3 Switching 

Port Mirroring Within a single switch Across all switches in stack 

Link Aggregation Within a single switch Across all switches in stack 

Stacking Link Typically Native Ethernet Proprietary interface or Ethernet 

Table 3: Comparison between Single IP Management and True Stacking 

4


Stacking Options by Product 

Due to physical differences (interfaces present/ 

available), options available for stacking the various 

Summit switches vary by product. 

Product Stacking Options 

Summit X250e SummitStack 

Summit X440 SummitStack 

SummitStack-V 





SummitStack-V80 


SummitStack-128 





Product Stacking Options 







Summit X670V SummitStack-V 

Table 4: Stacking Options by Product 



SummitStack Topologies 

Figure 1 illustrates the differences between a stack, 

a stack topology and an active topology. A stack is 

the collection of all nodes that are cabled together 

in a stack. A stack topology is the set of contiguous 

nodes that are powered up and communicating with 

each other. Switch 8 is not part of the stack topology 

in Figure 1 because it is not powered up. An active 

topology is the set of contiguous nodes that are 

active. An active node is powered up, configured for 

SummitStack operation, and communicating with the 


other active nodes. Switch 5 in Figure 1 has failed, and 

stacking is disabled on Switch 6 and Switch 7. Switch 

8 has no power, so the active topology includes the 

following switches: Switch 1, Switch 2, Switch 3, 

and Switch 4. 

Stack 

Stack 

Topology 

Active 

Topology 

Switch 1 

Switch 2 

Switch 3 

Switch 4 

Switch 5 

Switch 6 

Switch 7 

Switch 8 

Figure 1: Stack vs. Stack Topology vs. Active Topology 

Ring Topology 

s 

s 

s 

s 

s 

s 

s 

Failed Node 


Disabled 


Disabled 

No Power 

5333-01 

SummitStack nodes should be connected to each 

other in a ring topology. In a ring topology, one link is 

used to connect to a node and the other link is used to 

connect to another node. The result forms a physical 

ring connection. This topology is highly recommended 

for normal operation. Figure 2 shows a maximal ring 

topology of eight active nodes. 

Figure 2: Eight Stacked Switches in the Preferred Ring 

Configuration 

5334-01 

Please note: while a physical ring connection may be 

present, a ring active topology only exists if all nodes in 

the stack are active nodes. 

s 

5


Daisy-Chain Topology 

Stackable switches may be connected in a daisy-chain 

topology. This is a ring topology with one of the links 

disconnected, 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 1, the 

nodes delineated as the active topology are operating 

in a daisy-chain configuration, even though there is 

physically a ring connection in the stack. 

Management Options 

One of the key drivers behind any virtual chassis 

technology like SummitStack is the reduction of 

network complexity. While collapsing the management 

of up to eight devices onto a single virtual chassis 

helps, Extreme Networks provides a number of 

options for managing that virtual chassis, including 

a web interface, Ridgeline, the Extreme Networks 

management system and CLI. 

Figure 3: ScreenPlay, the Web Management Interface Built into 

ExtremeXOS 

Figure 4: Ridgeline Stack Management 


Configuring a New Stack 

Before deploying a new stack, consider the 

following guidelines: 

• Plan to use the stack as if it were a single multislot 

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 2). Only 

include the nodes that are intended to be active 

in the stack. To see the recommended procedures 

for installing and interconnecting a stack, refer to 

the hardware documentation. 

You can physically connect the stack to your networks 

before the nodes are configured. However, the default 

configuration on a non-stacking mode switch assumes 

a default untagged VLAN that contains all switch ports. 

When first powered on, the switch acts as a Layer 2 

switch, possibly resulting in network loops. 

• Make sure all nodes support the SummitStack 

feature and are running the same ExtremeXOS 

software version. To view the ExtremeXOS 

software version on a node, restart the node and 

run the command showversion {detail | process 

|images {partition } {slot 

} }. If any of the nodes do not have 

the right version, install the correct version 

on that switch. 

• Extreme Networks recommends that you use the 

same image partition on all nodes. Once stacking 

is enabled, an image upgrade from the stack is 

possible only if the same image is selected on 

all nodes. 

• If you intend to deploy new units that might be 

part of a stack in the future, you may want to 

turn on stacking mode during initial deployment 

to avoid a future restart. The disadvantages 

of stacking mode are the loss of the two QoS 

profiles QP6 and QP7 and the reservation of 

some of the packet buffer space for stacking 

control traffic. 

6


• You can configure the stack by logging into the 

master or any of the other nodes. 

• If the stackable switches have different purchased 

license levels, you may need to configure license 

level restrictions on some nodes before those 

nodes can join the stack. 

• Most stacking specific configurations are effective 

only after a restart (see Table 2). However, most 

non-stacking configuration commands take effect 

immediately and require no restart. 

• A basic stack configuration can be achieved by 

using the procedure described in the “About Easy 

Setup” section below. 

About Easy Setup 

Using Easy Setup, you can configure a stack without 

entering many of the stacking CLI commands. Easy 

Setup provides you an easy way to configure the 

required stacking parameters for all nodes. 

The Easy Setup procedure creates a stack with a 

master and a backup. The remaining nodes are 

configured with the master capability disabled. 

Extreme Networks recommends that you configure the 

stacking license restriction, if needed, before invoking 

Easy Setup. Otherwise, an additional stack reboot 

might be needed. 

The configuration procedure described in the next 

section starts Easy Setup. You can also start Easy Setup 

by entering Configure stacking easy-setup. Easy Setup 

performs the functions of the following five commands 

required to configure and activate the stack: 

• Enable stacking 

• Configure stacking slot-number automatic 

Figure 5: Easy Setup Configuration 

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• Configure stacking mac-address 

• Configure stacking redundancy 

• Minimal reboot stack-topology 

In a daisy-chain topology (which is not recommended), 

Easy Setup instead designates the node at the 

beginning of the chain as the master, and executes the 

command configure stacking redundancy none. 

Summary and Conclusion 

SummitStack offers powerful features enabling up 

to eight Extreme Networks Summit switches to be 

combined as a single virtual chassis. This allows for 

simpler, easier management as well as scalability. The 

“mix-and-match” capabilities of the SummitStack 

feature enable greater deployment flexibility. 

Available in both SummitStack and SummitStack 

V, Extreme Networks stacking can take advantage 

of special proprietary cabling as well as standard 

Ethernet connectivity. With a variety of management 

mechanisms available, including “easy-setup,” 

configuration is quick and straightforward. 

Europe, Middle East, Africa 

and South America 

Phone +31 30 800 5100 

Asia Pacific 

Phone +65 6836 5437 

Latin America 

Phone +52 55 5557 6465 

www.extremenetworks.com 

© 2012 Extreme Networks, Inc. All rights reserved. Extreme Networks, the Extreme Networks Logo, BlackDiamond, Direct Attach, ExtremeXOS, Ridgeline, 

Summit, SummitStack and XNV are either registered trademarks or trademarks of Extreme Networks, Inc. in the United States and/or other countries. 

Specifications are subject to change without notice. 1346_02 07/12

SummitStack Technical Brief - Extreme Networks

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