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
802.1ad adds a service tag outside the customer's tag. The calculator shows the overhead. It does not configure a switch. Both ends of the service link must agree which tag is the outer one. A customer tag that collides with your outer tag is a leak or a drop.
One service link you administer. Write the outer id and the customer range you will carry. Do not accept every customer VLAN because the command is shorter. Do not set it during the reading.
The extra tag reduces the payload. The MTU note belongs in the same ticket.
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 two ends.
- Pick the outer tag.
- List the customer VLANs you will carry.
- Write the extra bytes.
- Do not configure the link.
- Stop.
Mistakes that outlive the command
Q-in-Q (802.1ad) Explained goes wrong in a small set of ways. The list is here so the ticket can forbid them before the window.
- Every customer VLAN allowed.
- An outer tag that matches a customer tag.
- MTU forgotten.
- Configuring during the reading.
- A link you do not administer.
Decisions to write down
One decision for Q-in-Q (802.1ad) Explained: Both ends are yours. The outer tag is unique. The customer list is explicit. The overhead is written. And nothing was configured.
Checks before you call it done
Confirm this before you call the change done: The link is written. The outer id is written. The customer range is written. The overhead is written. And no switch was changed. If one of those fails, stop.
Before you leave the device
Q-in-Q (802.1ad) 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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