Change a stack

Before you start

• A District Administrator turns on Change stacks from the switch page in Settings › System › Features. It needs Let Cenovel change switch ports on too, and is off until then.
• The stack must be answering Cenovel, with a working SSH credential and a trusted host key. Cisco IOS XE stacks, Juniper Virtual Chassis and Extreme Switch Engine stacks are covered. Fabric Engine has no stack to change.
• A change is offered for a platform only once it has been proven against an emulated stack of that platform. A change that isn’t yet says so, and nothing is sent. The switches’ own prompts and the restart times below are still to be confirmed on real stacks, so try a change on a lab stack before you turn this on.

Who can make which change

A change that restarts members is a restart-class change: only a District Administrator makes one, and only after typing the switch’s name. Cenovel never switches a stack over, never restarts the primary, active or master, and never changes stack ports, roles or split detection; use the terminal at the switch for those.

Make a change

1. On the switch page, choose Change the stack in the Stack slots card. The drawer opens on Members: each member’s number, role, serial and priority.
2. Under What to change, choose Priority, Replacement, Renumber, Swap numbers or Copy settings. Only the changes you may make on this platform are offered. For a renumber, New number lists the free numbers and says what each still holds: a number set up for a model, or port settings kept for it.
3. Choose Preview the change. The review says, under What it takes, whether the switch undoes the change by itself, which members restart and for about how long, and when it takes effect. What changes lists every member and number affected, and the commands Cenovel would send are shown in full.
4. Give a reason if you like. For a restart-class change, or any change on Switch Engine (which has no undo of its own), type the switch’s name in Type the switch’s name to confirm.
5. Choose Apply, or Apply and restart. Applying follows each step; when it is done, What happened says what the stack read back.

How a restart-class change runs

• Checked first. Before anything is sent, Cenovel reads the stack again and refuses if a member is away, if the member is the primary, active or master, if a unit can’t be told apart by its serial or hardware address, or if the number asked for is taken. It refuses too if it can’t tell how it reaches the switch, or reaches it only through the members that would restart. On Switch Engine, each node needs an alternate IP address first.
• One member at a time. Each step sends the change, restarts that member, and waits for it to rejoin under its new number before the next step. A swap goes through the highest spare number: three restarts.
• Port settings stay with the numbers, not the units. A port’s configuration belongs to its member number, so after a renumber the unit takes on the settings kept for its new number. The review says so.
• No undo by more restarts. If a step fails before the member restarts, Cenovel puts back the stored number and nothing restarts. If a member hasn’t rejoined 15 minutes after its restart, the change ends Timed out: Cenovel stops, says how the stack reads and what wasn’t sent, and asks someone to check the unit at the closet.
• The record follows. When a unit rejoins under a new number, its stack record moves with it, so the Members card doesn’t call it missing.

Every change is audited before anything is sent, under a maintenance window. A refused change is audited too, with the reason, such as a name that wasn’t typed.

What each platform takes

See also: Work with a switch or stack · What Cenovel may change on a device · Change a switch port