About stack management

Components of Switch stack management

Stacking definitions

Term	Definition
Stack	Consists of a Commander switch and any Member switches belonging to that Commander's stack.
Commander	A switch that has been manually configured as the controlling device for a stack. When this occurs, the switch's stacking configuration appears as `Commander`.
Candidate	A switch that is ready to join (become a Member of) a stack through either automatic or manual methods. A switch configured as a Candidate is not in a stack.
Member	A switch that has joined a stack and is accessible from the stack Commander.

A switch moving from Candidate to Member

General stacking operation

After you configure one switch to operate as the Commander of a stack, additional switches can join the stack by either automatic or manual methods. After a switch becomes a Member, you can work through the Commander switch to further configure the Member switch as necessary for all of the additional software features available in the switch.

The Commander switch serves as the in-band entry point for access to the Member switches. For example, the Commander's IP address becomes the path to all stack Members and the Commander's Manager password controls access to all stack Members.

Stacking with one commander controlling access to wiring closet switches

Interface options

You can configure stacking through the switch's menu interface, CLI, or the WebAgent For information on how to use the WebAgent to configure stacking, see the online help by clicking on the ? in the WebAgent screen.

Operating rules for stacking

General rules

Stacking is an optional feature (enabled in the default configuration) and can easily be disabled. Stacking has no effect on the normal operation of the switch in your network.
A stack requires one Commander switch. (Only one Commander allowed per stack.)
All switches in a particular stack must be in the same IP subnet (broadcast domain). A stack cannot cross a router.
A stack accepts up to 16 switches (numbered 0-15), including the Commander (always numbered 0).
The stacking feature supports up to 100 switches in the same IP subnet (broadcast domain), however, a switch can belong to only one stack. In the event that the 100 switch limit is exceeded, it may take multiple attempts to add or move a member to any given stack. Once a member is added to a stack, it is not "forgotten" by the Commander.
The stack status (all) command will display up to 100 devices. Devices that are not members of a given stack may periodically drop out of the list.
If multiple VLANs are configured, stacking uses only the primary VLAN on any switch. In the factory-default configuration, the DEFAULT_VLAN is the primary VLAN. (See Stacking operation with multiple VLANs configured and The primary VLAN.)
Stacking allows intermediate devices that do not support stacking. This enables you to include switches that are distant from the Commander.

A non-stacking device used in a stacking environment

Specific rules

Specific rules for commander, candidate, and member switch

IP Addressing and Stack Name Number Allowed Per Stack Passwords SNMP Communities

Commander

	IP Addressing and Stack Name	Number Allowed Per Stack	Passwords	SNMP Communities
Commander	`IP Addr:` Requires an assigned IP address and mask for access via the network. `Stack Name:` Required	Only one Commander switch is allowed per stack.	The Commander's Manager and Operator passwords are assigned to any switch becoming a Member of the stack. If you change the Commander's passwords, the Commander propagates the new passwords to all stack Members.	Standard SNMP community operation. The Commander also operates as an SNMP proxy to Members for all SNMP communities configured in the Commander.
Candidate	`IP Addr:` Optional. Configuring an IP address allows access via Telnet or WebAgent while the switch is not a stack member. In the factory default configuration the switch automatically acquires an IP address if your network includes DHCP service. `Stack Name:` N/A	n/a	Passwords optional. If the Candidate becomes a stack Member, it assumes the Commander's Manager and Operator passwords. If a candidate has a password, it cannot be automatically added to a stack. In this case, if you want the Candidate in a stack, you must manually add it to the stack.	Uses standard SNMP community operation if the Candidate has its own IP addressing.
Member	`IP Addr:` Optional. Configuring an IP address allows access via Telnet or WebAgent without going through the Commander switch. This is useful, for example, if the stack Commander fails and you need to convert a Member switch to operate as a replacement Commander. `Stack Name:` N/A	Up to 15 Members per stack.	When the switch joins the stack, it automatically assumes the Commander's Manager and Operator passwords and discards any passwords it may have had while a Candidate. `Note:` If a Member leaves a stack for any reason, it retains the passwords assigned to the stack Commander at the time of departure from the stack.	Belongs to the same SNMP communities as the Commander (which serves as an SNMP proxy to the Member for communities to which the Commander belongs). To join other communities that exclude the Commander, the Member must have its own IP address. Loss of stack membership means loss of membership in any community that is configured only in the Commander.

IP Addr: Requires an assigned IP address and mask for access via the network.

Stack Name: Required

Only one Commander switch is allowed per stack.

The Commander's Manager and Operator passwords are assigned to any switch becoming a Member of the stack.

If you change the Commander's passwords, the Commander propagates the new passwords to all stack Members.

Standard SNMP community operation. The Commander also operates as an SNMP proxy to Members for all SNMP communities configured in the Commander.

Candidate

IP Addr: Optional. Configuring an IP address allows access via Telnet or WebAgent while the switch is not a stack member. In the factory default configuration the switch automatically acquires an IP address if your network includes DHCP service.

Stack Name: N/A

n/a

Passwords optional. If the Candidate becomes a stack Member, it assumes the Commander's Manager and Operator passwords.

If a candidate has a password, it cannot be automatically added to a stack. In this case, if you want the Candidate in a stack, you must manually add it to the stack.

Uses standard SNMP community operation if the Candidate has its own IP addressing.

Member

IP Addr: Optional. Configuring an IP address allows access via Telnet or WebAgent without going through the Commander switch. This is useful, for example, if the stack Commander fails and you need to convert a Member switch to operate as a replacement Commander.

Stack Name: N/A

Up to 15 Members per stack.

When the switch joins the stack, it automatically assumes the Commander's Manager and Operator passwords and discards any passwords it may have had while a Candidate.

Note: If a Member leaves a stack for any reason, it retains the passwords assigned to the stack Commander at the time of departure from the stack.

Belongs to the same SNMP communities as the Commander (which serves as an SNMP proxy to the Member for communities to which the Commander belongs). To join other communities that exclude the Commander, the Member must have its own IP address. Loss of stack membership means loss of membership in any community that is configured only in the Commander.


	NOTE: In the default stack configuration, the Candidate `Auto Join` parameter is enabled, but the Commander `Auto Grab` parameter is disabled. This prevents Candidates from automatically joining a stack prematurely or joining the wrong stack (if more than one stack Commander is configured in a subnet or broadcast domain). If you plan to install more than one stack in a subnet, Hewlett Packard Enterprise recommends that you leave `Auto Grab` disabled on all Commander switches and manually add Members to their stacks. Similarly, if you plan to install a stack in a subnet (broadcast domain) where stacking-capable switches are not intended for stack membership, you should set the `Stack State` parameter (in the Stack Configuration screen) to `Disabled` on those particular switches.

Stacking operation with multiple VLANs configured

Stacking uses the primary VLAN in a switch. In the factory-default configuration, the DEFAULT_VLAN is the primary VLAN. However, you can designate any VLAN configured in the switch as the primary VLAN. (See The primary VLAN.)

When using stacking in a multiple-VLAN environment, the following criteria applies:

Stacking uses only the primary VLAN on each switch in a stack.
The primary VLAN can be tagged or untagged as needed in the stacking path from switch to switch.
The same VLAN ID (VID) must be assigned to the primary VLAN in each stacked switch.

Status messages

Stacking screens and listings display these status messages:

Message	Condition	Action or Remedy
Candidate Auto-join	Indicates a switch configured with Stack State set to `Candidate`, `Auto Join` set to `Yes` (the default) and no Manager password.	None required
Candidate	Candidate cannot automatically join the stack because one or both of the following conditions apply: Candidate has `Auto Join` set to `No`. Candidate has a Manager password.	Manually add the candidate to the stack.
Commander Down	Member has lost connectivity to its Commander.	Check connectivity between the Commander and the Member.
Commander Up	The Member has stacking connectivity with the Commander.	None required.
Mismatch	This may be a temporary condition while a Candidate is trying to join a stack. If the Candidate does not join, then stack configuration is inconsistent.	Initially, wait for an update. If the condition persists, re-configure the Commander or the Member.
Member Down	A Member has become detached from the stack. A possible cause is an interruption to the link between the Member and the Commander.	Check the connectivity between the Commander and the Member.
Member Up	The Commander has stacking connectivity to the Member.	None required.
Rejected	The Candidate has failed to be added to the stack.	The candidate may have a password. In this case, manually add the candidate. Otherwise, the stack may already be full. A stack can hold up to 15 Members (plus the Commander).

SNMP community operation in a stack

Community Membership

In the default stacking configuration, when a Candidate joins a stack, it automatically becomes a Member of any SNMP community to which the Commander belongs, even though any community names configured in the Commander are not propagated to the Member's SNMP Communities listing. However, if a Member has its own (optional) IP addressing, it can belong to SNMP communities to which other switches in the stack, including the Commander, do not belong. For example:

An SNMP community operation with stacking

SNMP management station access to members via the Commander

To use a management station for SNMP Get or Set access through the Commander's IP address to a Member, you must append @sw <switch number> to the community name. For example, in An SNMP community operation with stacking, you would use the following command in your management station to access Switch 1's MIB using the blue community:

snmpget MIB variable 10.31.29.100 blue@sw1

Because the gray community is only on switch 3, you could not use the Commander IP address for gray community access from the management station. Instead, you would access switch 3 directly using the switch's own IP address. For example:

snmpget MIB variable 10.31.29.15 gray

In the above example ( An SNMP community operation with stacking) you cannot use the public community through the Commander to access any of the Member switches. For example, you can use the public community to access the MIB in switches 1 and 3 by using their unique IP addresses. However, you must use the red or blue community to access the MIB for switch 2.

snmpget MIB variable 10.31.29.100 blue@sw2

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