Configuring a stack

Creating a stack

Ways to create a stack include:

By the sequence in which the switches are booted. You choose which member becomes Commander.
Plug-and-go method. Ensure that stacking is enabled on all the switches, and then connect them together in the desired stacking topology. The plug-and-go method lets stacking decide which member is the Commander.

Using a deterministic method

Install a Stacking Module into an HP 3800 switch and then boot the switch, as described in the HP 3800 Switch Installation and Getting Started Guide.
Make sure that stacking is enabled for the switch:
1. Enter the show stacking command.
2. If stacking is disabled, enter stacking enable (in global config context). This command causes the switch to reboot.

When the switch finishes booting, enter the show stacking command again. The switch now has the status of Commander. It has a Member ID of 1 (one) and a default priority of 128.

Viewing show stacking output

HP Stack 3800#: show stacking
Stack ID : NO ID - will merge upon connectivity
MAC Address : 1cc1de-4d48c0
Stack Topology : No Stack Formed
Stack Status : No Stack Formed
Uptime : 0d 0h 5m
Software Version : KA.15.03
Mbr
ID Mac Address Model Pri Status
--- ------------- ------------------------------------- --- -------
1 1cc1de-4d48c0 HP J9574A 3800-48G-PoE+-4SFP+ Switch 128 Commander

To generate a stack ID, enter the following command:
```
HP Switch(config)#:stacking set-stack
```
(Optional) To have this switch retain its function as Commander through stack boots and other situations, you can increase its priority. The switch with the highest priority becomes Commander when all the switches are booted simultaneously. The default priority is 128. The priority can be set to any value between 1 and 255. To increase the switch’s stacking priority, enter the following command:
```
HP Switch(config)#: stacking member 1 priority 255
```
(Optional) Pre-configure (provision) the stack for the other switches that become members of the stack. You can assign a member number and a priority by entering the following command for each switch:

HP Switch(config)#: stacking member N type JxxxxA [mac MAC-Addr]
where:
- N is the stacking member number for the switch
- JxxxxA is the product number of the switch (required). Any of the HP 3800 models can be installed and assume this provisioned configuration. If you specify a value for this parameter, then only a switch of this specific model type can assume this provisioned configuration
- (Optional) MAC-Addr can be specified if you want a specific switch to assume this provisioned configuration. If this value is entered, then the type value for the switch that has this MAC address must be correct, or a configuration error is logged and the switch is not allowed to join the stack.
Connect the stacking cables to the module ports for the desired stacking topology. For example, plug port 1 and 2 in a ring.

Install Stacking Modules into the other switches that will be members of the stack, but do not boot them yet.


	NOTE: It is highly recommended that you create a mesh topology for maximum throughput and resiliency of the stack. At a minimum, a ring topology should be created. A chain topology is not recommended because any hardware or software failure in the stack results in lost ports, which increases the amount of time for the recovery of full stack operation due to multiple reboots. See the HP 3800 Installation and Getting Started Guide for supported topologies.

Boot the Standby and Member switches. The second switch that is booted becomes the Standby. The remaining switches become Members when booted.
When all of the switches are booted, enter the show stacking command to confirm that the stack is operating correctly. The following example shows four switches in a meshed topology.

Viewing output for four switches in a mesh topology

HP Stack 3800#: show stacking
 Stack ID         : 00031cc1-de4d48c0
 MAC Address      : 1cc1de-4d48c9
 Stack Topology   : Mesh
 Stack Status     : Active
 Uptime           : 1d 2h 35m
 Software Version : KA.15.05

  Mbr
  ID  Mac Address   Model                                  Pri Status
  --- ------------- -------------------------------------- --- ---------------
  1   1cc1de-4d48c0 HP J9574A 3800-48G-PoE+-4SFP+ Switch   250 Commander
  2   1cc1de-4d8680 HP J9573A 3800-24G-PoE+-2SFP+ Switch   230 Standby
  3   1cc1de-4e3180 HP J9574A 3800-48G-PoE+-4SFP+ Switch   128 Member
  4   78acc0-3c2180 HP J9576A 3800-48G-4SFP+ Switch        128 Member

Using the plug-and-go method

Install a Stacking Module into an each HP 3800 switch that will be in the stack, as described in the HP 3800 Switch Installation and Getting Started Guide, but do not connect them together with stacking cables yet

Make sure that stacking is enabled for each switch.

You can determine this by connecting a console to each switch and entering the command show stacking from the switch CLI.
If stacking is disabled, enter the command stacking enable. This command causes the switch to reboot.


	NOTE: By default, stacking is enabled on all the HP 3800 switches when a Stacking Module is installed before the switch is powered up for the first time, but if the switches were powered up without a Stacking Module installed, then stacking is disabled

If you are connecting stacking cables during/after switch boot, then multiple stacks can form (plug-and-go method).

Connect the stacking cables between the switches to form the desired stacking topology, then power on all switches.

When the switches that are stacked together complete booting up, one of the switches is elected as the Commander, one of the switches is elected as the Standby, the remaining switches become Members of the stack, and the stack becomes fully operational.

To find out the roles of the switches in the stack, connect a console to any of the switches and enter the show stacking command. You can use the MAC address and other information in the display to determine the roles of each of the switches.

Adding a switch to a stack as a new member

HP Networking stacking allows for switches to be added to the stack while the stack is operational (as long as the maximum number of 10 switches in the stack is not exceeded).

Provision the stack for the new switch by entering the following command:

HP Switch(config)#: stacking member N type JxxxxA [mac MAC-Addr]

where:

N is the stacking member number for the switch

JxxxxA is the product number of the switch (required). Any of the HP 3800 models can be installed and assume this provisioned configuration. If you specify a value for this parameter, then only a switch of this specific model type can assume this provisioned configuration

(Optional) MAC-Addr can be specified if you want a specific switch to assume this provisioned configuration. If this value is entered, then the type value for the switch that has this MAC address must be correct, or a configuration error is logged and the switch is not allowed to join the stack.
(Optional) You can pre-configure a priority for the member switch by entering this command:
HP Switch(config)#: stacking member N priority 100
Where:

N is the stacking member number for the switch.

X is the priority (1 - 255, but it should be less than the priority assigned to the Commander. The priority for the Standby should be the second highest in the stack. The member switches can be left at the default priority value of 128.)

NOTE: You must configure the type and the priority separately.
NOTE: When the new switch has been provisioned in the stack, a complete configuration can be applied to the switch even before it is physically connected to the stack, connected to the network, and powered up.

Power on the new switch. The new switch does not become a member of the stack unless stacking has been enabled on the switch.
Install a Stacking Module into the new switch, connect the switch into the stack via the stacking cables, and form the desired stacking topology.
When the switch has finished booting, establish a console session with it and, from the config context, issue the command to enable stacking:
```
HP Switch(config)#: stacking enable
```
This causes the switch to reboot. When the reboot is complete, the switch is a member of the stack with the attributes that you provisioned for it.
Confirm that the switch is now a member of the stack by issuing a show stacking command via a console session with any of the switches in the stack. The command output should show that the new switch is a Standby or Member of the stack with the member number and priority that you assigned to it.

When you add the switch to the stack, the following occurs:

The Stack Revision Number is incremented by one.
The Commander verifies that the new switch has the same switch software as the other switches in the stack, and downloads the software to the new switch if it does not. When downloading new software, there will be an automatic reboot during this process.
A stack ID is assigned, even if the switch is later disconnected from the stack.
The member's console is automatically redirected to the Commander.
The OOBM IP address for that member is no longer reachable.

Removing a switch from the stack

You can remove a switch from the stack to be redeployed in another part of the network. The procedures vary depending on whether the switch is the Commander of the stack or not.

Removing a Member or the Standby

Establish a console session with the stack via direct console cable connection or telnet. If using the console cable, connect it to the Standby.
Enter the following command to remove the switch from the stack:

HP Stack 3800(config)#: stacking member N remove

This causes the switch to lose its complete configuration and to be removed from the stack configuration. A subsequent show stacking command issued to the stack will show that the removed switch no longer exists in the stack.
Power down the removed switch.
Disconnect the stacking cables from the removed switch and from the other switches in the stack.

Removing the Commander

Establish a console session with the stack via direct console cable connection or telnet. If using the console cable, connect it to a switch other than the Commander
Enter the following command to force the Commander status over to the Standby switch:

HP Stack 3800(config)#: redundancy switchover

This results in the Standby switch taking the role of the Commander and a new Standby being selected from the remaining member switches. The former Commander becomes a Member of the stack.
To remove the former Commander from the stack:

HP Stack 3800(config)#: stacking member N remove

where N is the member number of the former Commander
Power down the removed switch.
Disconnect the stacking cables from the removed switch and from the other switches in the stack.

Renumbering stack members

If you did not provision the stack for the switches when you first created the stack, it is possible that members did not acquire the desired member numbers. The stack members can be renumbered.

A five-member stack is used in the following example with switches A, B, C, and D. These switches are members 1, 2, 3, and 4, respectively. Switch B acquired member number 3 and switch C acquired member number 2.

In the global config context, enter the remove command option for switch B (member 3) and switch C (member 2):
```
HP Stack 3800(config)#: stack member 3 remove HP Stack 3800(config)#: stack member 2 remove
```
All configurations on the removed member switch are deleted, not just the stacking configuration.
Enter the following command:

HP Stack 3800(config)#: stack member 2 type B's type mac-address B's MAC address

This command clears the MAC address of the member 2 configuration to allow switch C’s MAC address to be entered in the next command, without a duplicate MAC address occurring in the stack.
Reboot switch B (new member 2) and then switch C (new member 3).
To confirm that each switch now has the desired member number, enter the show stacking command.

Restoring the operation of a stack

Restoring operation after disconnecting a power cord

If a power cord becomes disconnected from one of the switches in the stack, the stack operation is affected. The stacking status of the switch that lost power is “Missing.” Its record is retained in the stack configuration. The effect of the power loss depends on the role of the switch in the stack.

If the Commander loses power, the Standby switch takes over as the Commander and one of the member switches in the stack is elected as the new Standby.
If the Standby loses power, one of the member switches in the stack is elected as the new Standby.
For any switch that loses power, all the network ports and stacking ports are non-operational until power is restored to the switch and it rejoins the stack. This affects the stacking topology.
Reconnecting the power cord restores the operation of the switch, however, if the switch was either the Commander or the Standby, then it returns in a different role if the topology has 3 or more members. In a 2-member stack, a Standby that reboots will rejoin as Standby.

Restoring operation after disconnecting a stacking cable

If a stacking cable becomes disconnected from one of the switches in the stack, the effect depends on the stacking topology that is being used:

Mesh—The stack topology is temporarily changed to a ring. To recover, simply reconnect the stacking cable; the mesh topology and the previous stack configuration is restored.
Ring—There is little effect. The stack topology is temporarily changed to a chain topology. To recover, simply reconnect the stacking cable; the ring topology and the previous stack configuration is restored.
Chain—The following occurs:
- The smaller section (fragment) of the stack that results from the disconnection becomes Inactive (the Stack Status value shown in the output of the show stacking command is Inactive.
- If the two resulting fragments are the same size, the fragment that contains the Commander will be Active, and the other fragment becomes Inactive.
- Both fragments will have a Commander and a Standby selected (if there is more than one switch in each fragment).
- When the stacking cable is reconnected to reform the chain:
  - The Commander and Standby of the Active fragment retain those roles for the resulting stack. If the original Commander was not in that fragment, then the stack will have a new Commander when the stack is reformed.
  - The switches in the Inactive fragment reboot and assume their new roles in the reformed chain.

Replacing a failed stack member

If a Stack Member fails, the effect on the stack depends on which member failed.

If the Commander fails, the Standby switch takes over as the Commander and one of the Member switches in the stack is elected as the new Standby. All network ports and stacking ports on the failed switch become non-operational.
If the Standby fails, one of the Member switches in the stack is elected as the new Standby. All network ports and stacking ports on the failed switch become non-operational.
If a Member fails, all network ports and stacking ports on that switch become non-operational.

If a Stack Member fails:

Physically remove the Stack Member from the stack.
Replace the failed Stack Member.

NOTE: HP recommends using the same type (product or "J" number) switch as a replacement since all configuration information is retained.

If you are using the same type switch as a replacement:
1. Provision the new switch using the stacking member N command.
2. Reconnect all Ethernet ports as they were on the failed switch.

If you are using a different type switch as a replacement:
1. Remove the failed switch from the stack configuration using the stacking member N remove command.
2. Provision the new switch using the stacking member N command.
3. Reconnect Ethernet ports and create a new stack configuration on the new switch.

If the replacement switch uses a different version of software, it will be updated automatically to match the software version running on the stack.

Replacing a failed stacking module

Replacing a failed stacking module is simpler than replacing a Stack Member since the switch configuration itself does not change. In this case, there is no need to re-provision the switch as a member of the stack. After you replace the stacking module, if the switch that experienced the module failure was Commander or Standby, the election of a new Commander and Standby is the same.

Merging stack fragments

When two fragments have the same stack-id, the merge of the fragments is almost always allowed regardless of the merge policy. The Commander and Standby of the merged stack are selected based on the election rules. All of the switches in the previously inactive fragment or fragments reboot, and then join the Active fragment as Members.

If both fragments are Inactive, then an election process occurs. The two (or more) Commanders in the fragments are compared. The Commander is selected using the following criteria:

Highest Stack Rev
If the stack rev is the same for both, then choose the switch with the highest configured priority
If the priorities are the same for both, then choose the switch with the highest OS revision
If the OS revisions are the same, then choose the switch with the longest uptime
If the uptimes are the same, then choose the switch with the lowest MAC address

Modifying the stack topology

You can increase the efficiency and redundancy of the stack by adding stacking cables to create a stacking mesh instead of a ring. This modification can be performed while the switches are powered on and the stack is operating. After connecting the cables, enter the show stack command. The Stack Topology field value displays the new topology.


	NOTE: Transitioning between mesh and ring topologies temporarily leaves the stack in an unsupported state (for example, when the stack is only connected to half of the additional ports). If a failure occurs during this time, redundancy is not guaranteed.

Downloading new software to the stack

The stack is essentially a single switch with the Commander unit controlling the management functionality, so the process of loading new software is identical to the process for a standalone HP 3800. See the Management and Configuration Guide for your switch.

After new software is loaded on the Commander, the Commander installs the software on all the stack members. The loading process can take some time.

To load the new software:

Load the new software onto the Commander via TFTP, USB, or Xmodem.
Once the new software is loaded, establish a console session with the stack and enter the following command:

HP Stack 3800#: boot system

This causes the entire stack to be rebooted. Each unit is booted from its image unless you specify otherwise with options to this command. Make sure that you boot from the image to which you downloaded (that is, primary or secondary). If you add a new member to an existing stack, the Commander updates the new switch’s software to match the current stack software. Multiple versions of software are not supported across stack members.
Confirm that the new software has been loaded on each stack member by entering the member-context command for each member. From the stack member context, you can see the switch software version that is running on that switch by entering the show flash or show version command.

Syntax:

member-context stack-member

Sets the CLI context so that subsequent commands apply to the stack member that is specified.


	NOTE: You must configure the type and the priority separately.


	NOTE: When the new switch has been provisioned in the stack, a complete configuration can be applied to the switch even before it is physically connected to the stack, connected to the network, and powered up.


	NOTE: HP recommends using the same type (product or "J" number) switch as a replacement since all configuration information is retained.

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