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
A private VLAN splits one subnet into an isolated set, a community, and promiscuous ports that may talk to both. The planner drafts the ids. It does not configure a switch. Isolated ports do not talk to each other. If a server must be reached, it sits on a promiscuous port you name.
One primary VLAN. The ports are ones you administer. Do not use this to hide a port from an administrator who should still reach it, and do not apply it during the reading.
The gateway, if the hosts must leave the VLAN, is a later ticket on the promiscuous side.
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 primary VLAN.
- List isolated, community, and promiscuous ports.
- Confirm the server is promiscuous if clients must reach it.
- Do not configure the switch.
- Stop.
Mistakes that outlive the command
Private VLANs Explained goes wrong in a small set of ways. The list is here so the ticket can forbid them before the window.
- Isolating the only server.
- A port you do not administer.
- Applying the VLAN during the reading.
- Two primaries in one window.
- No map of which ports may talk.
Decisions to write down
One decision for Private VLANs Explained: The switch is yours. The talking pairs are written. The server is reachable on paper. Nothing was configured. And one primary is the scope.
Checks before you call it done
Confirm this before you call the change done: The primary id is written. The port roles are written. The server port is named. No switch was changed. And a second primary was not added. If one of those fails, stop.
Before you leave the device
Private VLANs 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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