This is an original planning guide. It is not a vendor manual, an official standard, or legal advice. Example addresses use documentation ranges. Review every command before you paste it.
What this hour is for
IPv6 subnetting is still a prefix length. A /64 is the usual LAN length because hosts expect it. Longer than /64 on a user LAN is a choice you must justify. Shorter than /64 is a block of LANs, not one LAN.
The splitter drafts child prefixes. The count calculator drafts how many of a given length fit. You check the first child and the last child. Overlap is still overlap.
2001:db8::/32 is the parent only in a note. A real parent is the prefix you were allocated. Do not invent one.
Write the LAN length and the infrastructure length separately. Mixing them is how a point-to-point and a user LAN get the same size by accident.
The change you can finish
Apply nothing during the writing of the note. When the lab window opens, it is one change on the device named in the ticket. Read the draft, then the device, then decide.
Rollback is the file or the revision you saved first. You do not invent a rollback after the only copy is gone.
- Name the parent you were given.
- Choose the child length.
- Split and read the first and last child.
- Count them.
- Mark /64 for user LANs unless the ticket says otherwise.
- Stop before any router is touched.
Mistakes that outlive the command
IPv6 Subnetting Explained goes wrong in a small set of ways. The list is here so the ticket can forbid them before the window.
- A user LAN longer than /64 without a reason.
- A documentation parent used in production.
- Overlapping children.
- A count that was not read.
Decisions to write down
One decision for IPv6 Subnetting Explained: The parent is allocated to you. The child length is written. The first and last children were read. And user LANs are /64 or the exception is written.
Checks before you call it done
Confirm this before you call the change done: The parent is real. The children do not overlap. The count matches the split. No router was configured. And the note does not use 2001:db8:: as a production prefix. If one of those fails, stop.
A /64 is the usual user LAN.
Read the first and last child.Before you leave the device
IPv6 Subnetting Explained ends when the hostname on the device matches the hostname in the ticket. If it does not, you are on the wrong box. Stop. A command that succeeded on the wrong box is not progress.
The draft stays a draft until a person has read the names in it. A generator does not log into the device and does not know which interface is the uplink. You delete a line that names a device, a zone, or a prefix you did not write down.
0.0.0.0/0 is not kept because a sample included it. A source you can say is the source you keep. 192.0.2.0/24, 198.51.100.0/24, 203.0.113.0/24, and 2001:db8::/32 are documentation. They belong in the note. They are not prefixes you type onto a production device because they appeared in a draft.
prompt-for-this is a reminder that a secret is missing. It is not a password, a key, a community string, or a pre-shared key you save in the ticket or in git. The real secret stays in the store.
One change is the window. A VLAN and a routing protocol and a VPN do not share it. If two things move and the result is wrong, you will not know which one did it. The next feature waits for its own page.
If the same step fails twice, stop for the day. The failure is the result. Adding a forum command beside a half-applied config produces a device nobody can rebuild. Restore the copy you took first.
A second person reads the device name and the change aloud. If they cannot find them in the ticket, the note is not done. Silence is not agreement. Then leave the device alone.
This page is a planning guide. It is not a vendor manual, not an official standard, and not a permission to touch a network you do not administer. The pillar guide owns the wider design. This page owns one lab proof.
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