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
CGNAT is the shared address space a provider uses between a subscriber and the public internet. 100.64.0.0/10 is that space. It is not a private LAN like 10.0.0.0/8, and it is not yours to advertise.
The checker labels an address you type. You type one address from a plan or a log you are allowed to hold. A label is not a permission to probe the address.
If a provider hands you an address in this range, your edge is behind their translation. Write that down before you design inbound services. Inbound from the internet will not reach you the way a public address would.
Do not use 100.64.0.0/10 as spare office space because it looked unused.
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.
- Type one address you may hold.
- Read the label.
- If it is CGNAT, write that the provider translates.
- Do not put the range in a LAN plan.
- Do not advertise it.
- Do not probe it.
Mistakes that outlive the command
What Is CGNAT (100.64.0.0/10)? goes wrong in a small set of ways. The list is here so the ticket can forbid them before the window.
- Using 100.64.0.0/10 as a private LAN.
- Advertising it upstream.
- Expecting inbound internet access on a CGNAT address.
- Probing an address because the checker labeled it.
Decisions to write down
One decision for What Is CGNAT (100.64.0.0/10)?: The address is one you may hold. CGNAT is not LAN space. Inbound design accounts for the translation. No advertisement. And no probe.
Checks before you call it done
Confirm this before you call the change done: The label is written. The range is absent from the LAN plan. Inbound was discussed. Nothing was advertised. And nothing was probed. If one of those fails, stop.
Before you leave the device
What Is CGNAT (100.64.0.0/10)? 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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