Cisco Systems SLM224G4PS manual Advanced Stacking, Stack Resiliency, Unit IDs, Unit ID Allocation

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Appendix B

About Switch Stacking

the Console port, Telnet or Web-based Utility) and reset the units to make this assignment permanent.

The unit that is assigned number 1 will act as the Master; this is indicated by the Stack Master LED on its front panel being lit amber. The unit that is assigned number 2 will act as the Backup Master.

Stack Resiliency

A stack’s topology may be either Ring or Chain. The best practice is to configure the stack in Ring topology, due to its higher resiliency in case of unit failure or stacking link failure.

Additionally, if a redundant power supply is used, it is recommended to make sure that the Master and Backup Master units are connected to the redundant power supply.

Advanced Stacking

In order to understand the operation of the stack it is necessary to understand two key concepts:

Unit IDs, and how they are allocated

Stack unit start up process

Unit IDs

Each unit in a stack has an assigned unique Unit ID number. Unit ID numbers are meaningful as follows:

The unit that is assigned Unit ID=1 will serve as the Stack Master. All other units will be stack members.

The stack Master provides a single point of control, configuration and management for the entire stack, and stores the configuration for all stack members (which themselves do not store any configuration information at all).

The unit that is assigned Unit ID=2 is a special stack member, which serves as the Stack Backup Master.

A stack Backup Master, in addition to being a stack member, serves as a Backup in case the stack Master fails or is disconnected for any reason. If that should happen, the Backup Master takes over the role of stack Master for the remaining stack members.

To make this possible, the stack Master will store a copy of the active configuration on the Backup Master, but this copy will only be used if and when it takes over the role of stack Master. Note that only the configuration file is copied. Any dynamically filled tables, e.g. addresses learned, are not copied from the Master to the Backup Master. If the Backup Master takes over the role of stack Master, it will start building its own dynamic tables from scratch.

Units that are assigned Unit IDs 3-6 (SLM224G4PS) or Unit IDs 3-4 (SLM248G4PS) are called Stack Members.

A stack member will only operate as a member of the stack under the direction of an operational stack Master (or a Backup Master that has taken over the role).

Stack members are not directly manageable and configurable, and must be managed through the stack Master, and do not contain any meaningful configuration information (not even their own configuration). If an operational master is not present and reachable, these units will not be functional.

Master Enabled units

Units that are assigned a unit ID number of 1 or 2 are calledmasterenabledunits.Onlymasterenabledunits participate in master election (see below) whenever they are initiated, inserted into a new stack or lose connectivity with the existing master. Only master enabled units can become the stack master or backup master. Units with assigned IDs of 3-6 (SLM224G4PS) or 3-4 (SLM248G4PS) can become neither a master nor a backup master unless this is done manually by the system administrator or they are reset to the factory default first.

Unit ID Allocation

Units are shipped from the factory with no Unit ID, and must be assigned a unique Unit ID before they can operate as part of a stack. Unit ID numbers are assigned to units in one of two ways:

Assigned by the system administrator, in which case they can only be changed manually by the system administrator

Allocated to a stack member unit by the stack Master during system initialization

In general, a unit that was assigned a Unit ID will tend to keep this number even after it is rebooted. The stack Master may reallocate Unit IDs during system initialization to resolve duplicate Unit ID conflicts (see below). Manually assigned Unit IDs cannot be changed by the stack Master, even if they are in conflict.

Unit ID assignment/change takes effect only during system initialization and does not take place during run- time of the system.

Units of a stack do not have to be numbered in sequence or in order, and may be interconnected as desired, as long as each unit has a unique ID and at least one unit of the stack serves as stack Master.

24/48-Port 10/100 + 4-Port Gigabit Smart Switch with Resilient Clustering Technology and PoE

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Contents Port or 48-Port 10/100 + Icon Descriptions About This GuideAbout This Guide Online ResourcesTable of Contents Snmp Snmp Global Parameters Snmp Views Snmp Group ProfileAppendix B About Switch Stacking Gigabit Ethernet Fiber Optic CablingAppendix C Glossary Appendix D Specifications Appendix G Contact InformationChapter IntroductionProduct Overview Switch LEDs and ports are located on the front panelChapter Product Overview Front PanelSwitch’s LEDs and ports are located on the front panel Power The Power port is where you connect the AC powerBack Panel Product Overview Pre-Installation Considerations Chapter InstallationInstallation Placement OptionsDesktop Placement Hardware InstallationRack-Mount Placement Configuring Stack Mode Uplinking the SwitchTo set up a stack with six switches, follow these steps Connect port G1 on Unit 2 to port G2 on Unit Power off the new unit 5 the former master unitConnect port G1 on Unit 3 to port G2 on Unit Using telnet Chapter Configuration Using Console InterfaceLogin screen appears. Proceed to the Login section below Switch Main Menu How to Use the Console InterfaceLogin System Configuration MenuManagement Settings System InformationSecurity Settings User & Password SettingsIP Configuration Http Stack Configuration Restore System Default SettingsReboot System File ManagementPort Configuration Port Status MenuHelp System ModePoE Settings LogoutSetup Summary Chapter Configuration Using Web-based UtilitySetup Device InformationOrange The administrator has closed down this port Setup ZoomSetup Network Settings Clicking on a port displays the Port Configuration screenLocal Time Setup TimeSet Time Daylight SavingPort Management Setup Stack ManagementPort Management Port Settings Sntp ServersPort Management Port Settings Port Configuration LAG Configuration Port Management Link AggregationPort Management PoE Power Settings Port Management LacpVlan Management Create Vlan Vlan Management Port SettingVlan Management Vlan TableVlan Management Vlan to Port Vlan Management Port to VlanJoin Vlan to Port Statistics Rmon Statistics StatisticsStatistics Rmon History Log Table Rmon HistoryRmon History Table Add Alarm Statistics Rmon AlarmsAlarm Table Statistics Port Utilization Statistics Rmon EventsStatistics Interface Statistics Ethernet-like Security 802.1x SettingsSecurity ParametersSetting Timer Security Port SecuritySecurity Management Access List Security Storm ControlSecurity Radius QoSBroadcast Only Counts only Broadcast traffic CoS Settings QoS CoS SettingsQoS Queue Settings CoS DefaultQoS Basic Mode QoS Dscp SettingsQoS Bandwidth Spanning Tree STP Status Global SettingSpanning Tree Spanning Tree Global STPBridge Settings Spanning Tree STP Port SettingsSpeed Displays the speed at which the port is operating Multicast Igmp Snooping Vlan Igmp SettingsMulticast Multicast Bridge MulticastMulticast Bridge Multicast Forward All Snmp Global ParametersSnmp Views Snmp Group ProfileSnmp Communities Snmp Group MembershipUser Name Provides a user-defined local user list Base Table Snmp Notification FilterSnmp Notification Recipient Advanced TableUser Authentication AdminAdmin User Authentication Local User EditAdmin Dynamic Address Admin Static AddressSecure The entry is defined for locked ports Query Admin Port MirroringAdmin Cable Test Clear Table If selected, this clears the MAC Address tableAdmin Save Configuration Admin Reboot Admin Firmware UpgradeAdmin Factory Default Admin Server Logs Admin LoggingAdmin Memory Logs Admin Flash Logs LogoutGigabit Ethernet Appendix aAppendix a About Gigabit Ethernet Fiber Optic Cabling Fiber Optic CablingAppendix B Appendix B About Switch StackingAbout Switch Stacking Stack Building Quick StartUnit IDs Advanced StackingStack Resiliency Unit ID AllocationMaster Discovery Stack Units Startup ProcessMaster Election Stacking Examples Unit and Port ConfigurationUser Controls Replacing a Failed Stack Member in a Running StackStack Master Failure and Replacement Subgroup Contains Both Master Unit and Backup Master Unit Splitting a StackMerging Two Stacks Both Stacks Kept Running During InsertionStacking Cable Failure Inserting Too Many UnitsAppendix C Glossary Appendix CGlossary Glossary Packet a unit of data sent over a network Mail protocol on the InternetAppendix C Specifications Appendix D SpecificationsAppendix D Dimensions Class of Service Port-based 802.1p Vlan priority-basedPower in compliance with Ieee Management VlanAppendix E Warranty InformationObtaining Warranty Service Exclusions and LimitationsWarranty Information Technical SupportAppendix F Regulatory InformationRegulatory Information Appendix F Norsk Norwegian Miljøinformasjon for kunder i EU Appendix F Appendix G Contact Information