- The document describes the stacking architecture and configuration of Marvell switches. Stacking allows multiple switches to be managed as a single unit. One switch acts as the master and controls the configuration of the entire stack. Switches connect to each other via stacking ports and can operate in a ring or chain topology with up to 6 switches per stack. The unit ID identifies each switch in the stack.

1. AT-8000S
Stacking Architecture
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2. Stacking Overview
• Multiple switches - single management.
• Management interfaces:
– Web-based Interface
– Command Line Interface (CLI)
– SNMP
• One Master, one Backup and multiple regular units.
• Each unit has a unique unit ID.
• All units must run the same major SW version.
• The Stack Master Switch maintains the configuration.
• On AT8000S/16 there is only standalone mode.
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3. Stack Topology
• Topologies supported:
– Ring
– Chain
• Up to six units per stack.
• The stack units are connected via 2 Giga ports.
– One port is the “uplink”
– Other port is the “downlink”
• One of the units acts as a stack master.
• All other units act as slaves.
• One of the slaves can also act as a master backup.
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4. Ring and Chain Topology
RING
Chain
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5. Unit ID
• Device Unit ID is unique.
• Assigned by the user.
• Units ID 1 and 2 are Master Enabled units.
• All the other units are regular units.
• A boot menu is available during the boot process to select
the Unit ID.
• Unit ID is displayed via console, SNMP or Web.
• Stack unit number can be 1-6.
• In standalone mode - Unit ID is 0.
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6. Unit ID Selection
Process
• System provides a boot menu to set unit stack ID (1-6).
• The menu is available during boot process.
• User has 2 seconds to abort image load and to enter the boot
menu.
• After device is running, unit ID can be modified by rebooting the
device, and using the boot menu.
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7. Unit ID – Boot Menu
Startup Menu
[1] Download Software
[2] Erase Flash File
[3] Password Recovery Procedure
[4] Enter Diagnostic Mode
[5] Set Terminal Baud-Rate
[6] Stack menu
[7] Back
Enter your choice or press 'ESC' to exit:
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8. Unit ID – Boot Menu
Stack menu
[1] Set unit number in stack
[2] Stack info
[3] Back
Enter your choice or press 'ESC' to exit:
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9. Viewing Unit ID - LED
• The unit ID is indicated in the device front panel.
• LED S# (1 till 6) indicates the unit number.
• If all LEDs 1-6 are off, the device operates in Standalone
mode.
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10. Viewing Unit ID - CLI
• A CLI command is available to view unit ID while unit is
running.
• User can choose to see unit ID indication on all stack units,
or on a specific unit only.
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11. Duplicate Unit ID
• A duplicate ID in a stack can occur if a user assigned the
same unit ID to more than 1 unit in the same stack.
• Only one unit will join the stack.
• The criteria are:
1. Longest uptime stays.
2. Least impact on the stack leaves.
• The LEDs of the unit that does not join will flash.
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12. Standalone Vs. Stack-Mode
Operation
• A unit can be in one of the following modes of operation:
– Standalone
– Stack-mode
• Determined at SW Boot phase.
• At factory default, units boot in stand-alone mode.
• Standalone units do not run any stacking applications.
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13. Stand Alone Mode
• The Standalone unit…
– Does not run the stacking application
– Does not participate with any stacking protocol
– Does not work as stack unit.
• To change a standalone to a stack unit:
– Restart the device
– Set the unit ID to 1-6
– Connect unit to stack
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14. Stack Unit Operation Modes
• A unit running in stack mode can operate as one of the
following:
– Master
– Regular stack unit
– Master Backup
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15. Master Unit Roles
• Manages the entire stack
• Responsible for the stack configuration
• Runs all protocols
• Updates and synchronizes the Backup master
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16. Slave Unit Roles
• Controlled by master
• Does not run high level protocols
• Will never take role of stack master
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17. Mater Backup Unit Roles
• Runs as slave unit, and in addition…
• Configuration files synchronized with master
• Monitors existence of master
• In case of failure takes over as stack master
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18. Master Election Process
• “Master Enabled” units:
– Only two Units at most
– UNIT ID is set to 1 or 2
• Master election algorithm will choose one of the two
“Master Enabled” units as stack master.
• The election algorithms criteria:
– System Up Time
– Lowest Unit ID
• The election process:
1. Master enable units exchange up time.
2. If up time difference between units is less than 10 minutes  the
unit with the lowest unit ID is elected.
3. If up time difference between units is more than 10 minutes  the
unit with the longest UP time is elected.
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19. Force Master
• User can “force” a master-enabled unit to be the master
unit.
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20. Master Failure Backup
• Master and Backup maintain a “Warm Standby” – if Master
fails, the Backup takes its place.
• “Warm Standby” means full synchronization with static
configuration.
– Configuration synchronization = running configuration + startup
configuration
• Dynamic configuration – is not maintained.
• On “switchover”, the Backup master:
– Restarts all protocols
– Reconfigures the stack
– Configuration synchronization = startup configuration + running
configuration
– Flushes all the packet processors tables
• A regular stack unit (unit ID 3-6) will never become a
master, even if no master enabled unit exist in stack
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21. Master Failure Backup
• When a unit transitions from “master” state to “backup”
state, it is automatically reset.
• If a Master-enabled unit inserted into a running stack…
– Is elected as a “Backup Master” (unless it’s uptime is bigger than
the current master)
– Already running Master will synchronize the new backup
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22. Stacking ports
• Standard copper GE located on the devices’ rear panel.
• Stacking ports are not available to user in “standalone”
mode as regular Network (Giga) ports.
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23. Hot Removal /Unit Failure
• Topology change event is caused by:
– Unit failure
– Unit hot insertion/extraction
– Stacking link failure/extraction/insertion
• Noticed and kept by the master
• Stack will continue to operate normally.
• Link state of failed unit ports will be set to down state.
• No service interruption to units that remained connected.
• Backup unit retains the configuration file even if it is
removed from the stack.
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24. Hot Removal / Unit Failure
• Unit failure can split the chain.
• If there is a Master and a backup in the system each chain
will function separately.
• The stack will split into two independent stacks.
1 Master
Stack 1
2 Slave
3 Slave
Unit Failure
4 Slave
Stack 2
5 Backup
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25. Newly Inserted Unit
• Stack port table:
– Held by the Master
– Includes the max number of ports the stack could handle
• For each unit, a range of ports is mapped according to its
Unit id.
• Replacing a unit type (same unit ID):
– Unit type is identical - the new Unit ports would be reconfigured
exactly as the old one
– New unit has lower/higher number of ports - only matching ports
will be reconfigured
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26. Stack Topology Changes
Different types of unit replacement
48 ports device replaces 24 ports device
SR248 replace SR224 24 ports SR224 replace SR248 device
device replaces 48 ports
Old Box Stack 1 Old Box
.....................
24 1 Stack 2...................
.. .
26. 25 48 ...........25,..24.
.... ...
24,25 1 .Stack49
5... 1
.0
Stack 2
Default Configuration
New Box New Box
5... 1
.Stack49
.0 .....................
24 1 Stack 1
26. 25
..
48……25 24……1 Stack 2 Stack 2
Marvell Confidential

27. Stack Configuration
• Configuration files are changed only through
explicit user action, and are not automatically
modified when units are added, removed,
reassigned unit ID’s or toggled from stack-mode
operation to standalone operation and back.
• The system “remembers” all configuration
information, even if it applies to ports/units that
were removed from the stack.
• Only ports physically present are displayed in the
Browser-based GUI, and thus only ports
physically present may be configured using this
interface.
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28. Stacking - CLI
Commands
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29. CLI Commands – Force Master
• Use the following Global Configuration mode command to
force a selection of specific unit to be stack master. Use the
“no” form of the command to return to default
configuration:
stack master unit unit
no stack master
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30. CLI Commands – Show Stack
• Use the following User EXEC mode command to display
stack status information:
show stack [unit]
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31. Stack Related CLI commands
• Use the following Privileged Exec mode command to boot
entire stack or specific unit in stack:
stack reload [unit]
• Use the following Privileged Exec mode command to define
the image to use at startup for stack units:
boot system [unit unit] {image-1 | image-2}
• Use the following Privileged Exec mode command to copy
a boot or image file from stack master to one of the stack
units:
copy image unit://unit_number/image
copy boot unit://unit_number/boot
• Use “*” to copy to all units:
copy image unit://*/image
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32. CLI Command - Show Stack
console# show stack
Unit Address Software Master Uplink Downlink Status
--------------------------------------------------------------------------------
1 00:00:b0:10:11:00 1.0.0.0 Enabled 3 2 master
2 00:21:03:08:52:30 1.0.0.0 Enabled 1 3 backup
3 00:00:28:02:05:11 1.0.0.0 Disabled 2 1 slave
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33. CLI Command - Force Master
console(config)# stack master unit 2
console(config)#
-----------------------------------
Unit rebooted: switchover to backup
-----------------------------------
**************************************************
***************** SYSTEM RESET *****************
…
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34. CLI Command - Force Master (Show)
console# show stack
Unit Address Software Master Uplink Downlink Status
--------------------------------------------------------------------------------
1 00:00:b0:10:11:00 1.0.0.0 Enabled 3 2 backup
2 00:21:03:08:52:30 1.0.0.0 Forced 1 3 master
3 00:00:28:02:05:11 1.0.0.0 Disabled 2 1 slave
console#
console# show running-config
interface ethernet 2/e24
ip address 30.1.1.1 255.0.0.0
exit
stack master unit 2
Marvell Confidential

35. CLI Command - Copy Command
console# copy image unit://*/image
01-Jan-2000 01:44:59 %COPY-I-FILECPY: Files Copy - source
URL flash://image destination URL Unit all flash://image
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!01-Jan-2000 01:46:59 %COPY-W-TRAP: The copy operation
was completed successfully
!
Copy: 4239439 bytes copied in 00:02:00 [hh:mm:ss]
Marvell Confidential

36. Marvell Confidential