Frequently asked questions on Auto-stacking
What is VSF auto-stacking?
VSF auto-stacking feature provides a mechanism to automatically form a stack when the stack members are physically connected in a desired topology. This reduces the user intervention touch points to form a VSF stack. You can add a new switch to the existing stack by physically connecting it to a member of the stack. A member ID is automatically assigned to the new switch and rebooted. After rebooting, the newly added member joins the stack.
Is it mandatory to connect the new switch in the direction of higher denomination master port only after configuring the VSF links on the master for auto-stacking?
Yes. Auto-stacking process always starts only in the direction of higher denomination port of the master. If no switches are connected to the higher denomination port, auto-stacking process will not start.
If a new switch added for stacking is connected in the direction of lower denomination port of the master, the master will show it as an error. Use the command to see the error and its recommendation to fix the error.
For example, the Switch2 and Switch will join the stack only when they are connected in the direction of higher denomination port of the master as shown in the following figure:
Can the size of the stack be extended in the direction of lower denomination port of the master?
No. You can still renumber manually and add the members to the stack. But the newly added member will not join the stack automatically through auto-stacking.
What are the different methods to designate the master to bring up a stack using auto-stacking?
There are five different ways to designate the master and bring up the stack using auto-stacking. The different ways are:
- Configuring the VSF links manually on the master switch.
- Executing the vsf start-auto-stacking command using CLI on the master switch.
- Pressing the Stk LED mode button on the master switch.
- Downloading full stack configuration using ZTP.
- Downloading full stack using TFTP, SFTP, NetEdit, or REST.
What happens when the master is designated manually by configuring lower denomination port as VSF port first?
This can potentially lead to formation of out-of-order stack since auto stacking happens only in the direction of highest denomination port. If physical connections are already made, the newly added switch might not join the stack.
What is the eligibility criteria for a switch to be connected to an existing stack through auto-stacking?
For a switch to connect to an existing stack, it must be in the auto-join eligible state. A switch in its factory default state is considered to be auto-join eligible.
When will a switch becomes auto-join eligible? Is there a way to make a switch auto-join eligible again to take part in the auto-join process to form the stack?
If a switch moves out of factory default configuration state, then the switch cannot join an existing stack.
In this case, use the vsf force-auto-join command to make a non-factory default switch to auto-join eligible again. Once the user sets force auto-join in the switch configuration, the switch will be considered as auto-join eligible and will join the stack even though the switch does not have factory default configuration.
vsf force-auto-join command will only work if the switch does not have any pre-existing VSF configurations such as secondary or VSF links. If the switch has VSF configurations already, then the recommendation is to unconfigure and reconfigure vsf force-auto-join once all VSF configurations are removed from the switch.
Is it mandatory to use only the internally reserved ports to bring up a stack through auto-stacking ?
No. If you need to form a stack using vsf start-auto-stacking command or by pressing Stk LED mode button, then it is mandatory to use the internally reserved VSF ports.
Based on the product type of a switch, the following two interfaces are reserved for the auto-stacking process:
- 24-port switch models: 25 and 26
- 48-port switch models: 49 and 50
However, if the stack is formed by any of the other methods , you must ensure that the physical interconnections on the stack ports between different members of the topology is matching with the provisioned configuration on the master.
Can a stack be formed through auto-stacking when the master is running on 10.07 firmware version and the newly added member is running on firmware version prior to 10.07?
No. It is mandatory to have all the switches running on 10.7 or later releases to form a stack through auto-stacking .
You cannot form a stack through auto-stacking if either master or the stack members running on different firmware versions prior to 10.07.
Will a stack be formed if the Stk mode button is pressed on all the members before physically connecting the cables?
No. Pressing the Stk mode button on all the members will configure VSF links and secondary on the switches which will make the members not eligible for auto-join. The members will join with the stack only when it becomes auto-join eligible again.
Pressing Stk LED mode button is to designate the master. So, press Stk LED mode button only on the switch which is supposed to be the master of the stack. There should be only one master for a VSF stack.
Will a stack be formed if vsf start-auto-stacking is executed on all the members before connecting the cables physically?
No. Executing the vsf start-auto-stacking command will configure VSF links and secondary on a switch which will make the switch not eligible for auto-join, The members will join with the stack only when they become auto-join eligible again.
Executing vsf start-auto-stacking is to designate the master. So, execute the command on the switch which is supposed to be the master of the stack. There should be only one master for a VSF stack.
What will happen if Stk mode button is pressed on the master of an active stack?
Since the VSF configurations are already present , pressing the Stk mode button will not have any effect on the stack configuration. But the LEDs of the stack will now glow to depict the state of the stack.
For more details on the LED states, Stack and Port LED states
What will happen if the vsf start-auto-stacking command is executed on the master of an active stack?
Since the VSF configurations are already present , configuring vsf start-auto-stacking will not have any effect on the stack configuration. An error message also will be displayed to show that the switch does not have factory default configuration.
After downloading the VSF stack configuration to the master through TFTP/ZTP/NetEdit, what happens if a new member added has a different SKU than the one provisioned for that particular member-id through auto-stacking?
If the existing stack size configuration is less than maximum size supported (10 for 6300 switch series, 8 for 6200 switch series) , the newly added member will join the stack with the least member-id available , but not with the provisioned member id.
If the existing stack size configuration is already the maximum size supported, then the newly added member will go for a reboot , but will not join the stack. This member will again come up with the factory default configuration as there is a SKU mismatch.
What happens if the Stk mode button is pressed when the cables are not connected properly on the reserved interfaces, later connected correctly on the reserved interfaces?
Members switches go for a reboot and join the stack when the cables are connected on the reserved interfaces correctly.
Is multi-port VSF configuration supported to bring up a VSF stack through auto-stacking?
Forming a stack using auto-stacking with multi-ports can be done only when the configuration of all the members are fully pre-provisioned on Member 1.
By default, Stk mode button press or vsf start-auto-stacking command configures only one port per VSF link. So even if multiple ports were connected physically, stack will come up with single port per VSF link only.
Can cables of different speed be connected to the members to form a stack through auto-stacking?
Yes. Though it is supported , it is always recommended to have the entire stack with cable of same speed for VSF links.
What happens when non-reserved ports of the newly added switch is connected to the auto-stacking reserved ports of member 1?
Newly added member will not go for a reboot unless there is a provisioned configuration of the member matching with non-reserved ports on member 1.
To use Stk mode button or vsf start-auto-stacking command, the cables must be connected to the reserved interfaces on the new switch to start the auto-stacking process. For more information on reserved interfaces, see Reserved interfaces for auto-stacking
Can the Stk mode button or vsf start-auto-stacking command be used on a switch which has some VSF configuration already?
No. To use Stk mode button or vsf start-auto-stacking command, the switch must be in factory-default configuration.
Is there a way to download configuration automatically after forming a stack via Stk mode button press?
Yes. Once the stack is formed , ztp force-provision will be automatically enabled on the stack. But you must have an uplink connectivity to DHCP Server (which can provide the ZTP options) and TFTP server to download the firmware and configuration files.
Can I download the full stack configuration via TFTP to the running configuration directly?
Full stack configuration can be downloaded into the master of the stack. The recommendation is to first download the configuration to the start-up and then move the startup to the running configuration. Copying the configuration first to startup will help in detecting errors in the deployed configuration. Once the configuration is copied to startup without any errors, then the startup configuration can be applied to the running configuration. This will also ensure that auto-stacking process did not start prematurely. The stacking process might start prematurely if the configuration is applied directly to the running configuration.
How to check whether the switch is auto-join eligible or not?
Executing the show vsf or show vsf details command shows an entry called Autojoin Eligibility Status which shows whether the switch is eligible or not eligible .
Is it possible to change the secondary member of the stack which is formed through vsf start-auto-stacking or stk mode button press?
Yes. You can execute the vsf secondary-member <member-id> on the master to change the secondary member. This will reboot the member 2 (default secondary) and make it to join the stack as member. Then the newly configured secondary member will go for a reboot and joins the stack as standby. Changing the secondary member can only be done from the primary switch (member 1).
Will the switch stay as auto-join eligible if any new VSF configurations are made after executing the vsf force-auto-join command?
No. vsf force-auto-join is a command used to make an auto-join ineligible switch to auto-join eligible again. If the VSF configuration of the switch gets changed again after executing the vsf force-auto-join command, the switch will become auto-join ineligible again. When the VSF configurations are removed , switch will automatically become auto-join eligible.
What happens if a member configuration is removed from the master of a stack using the no vsf member <id> command?
If the member is part of the stack (not in “Not Present” state) and its ports are connected through reserved auto-stacking ports, then the removed switch will join back the stack after it comes up as standalone. This is because the auto-stacking starts on the reserved ports. So, after member removal, make sure you immediately disconnect the cables physically as well.
Will both auto-stacking and ZTP process start simultaneously if the master is designated using the configuration download through ZTP,?
No. The auto-stacking process will start only after the completion of ZTP process.
Is there any difference between forming the stack using the vsf start-auto-stacking command and Stk mode button?
There is no difference in forming the stack. But the ztp force-provision configuration will be added in addition to the VSF related configurations only when the stack is formed using the Stk mode button press. If the stack has an uplink connectivity to DHCP server, then the configuration and firmware for the stack can be downloaded from a TFTP server through ZTP.
Does auto-stacking support ring topology without the need for any configuration changes?
Yes. By default, auto-stacking feature configures two links on each of the VSF members. In case, if there is a need to change the stack from chain to ring topology, connect the first member with the last member of the stack with a cable on the auto-stacking reserved ports.
For example, consider the three-member stack in a chain topology as shown in the following figure:
To change this into ring topology, connect Switch3 and Switch1 as shown in the following figure:
The three-member VSF Stack in chain topology can also be converted into a four-member VSF stack in Ring topology by connecting the Switch4 to port 1/1/50 of Switch3 and port 1/1/49 of Switch1 as shown in the following figure:
Can I use reserved auto-stacking interfaces as normal data ports?
Yes. The reserved auto-stacking interfaces can be used as normal data ports.
