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
An ACL decides in order. The first matching line wins. A later deny does not repair an earlier permit any. The hit simulator drafts which line matches a flow you type. The shadow finder drafts lines that can never match. Neither tool loads a router.
A permit of any to any is a line you do not keep. A list applied in the wrong direction is a different list. Write the interface and the direction.
Do not apply a list to the session you are using until a second session is open. The vendor how-to is that lab. This page is the reading.
Log lines can contain addresses you should not paste into a public ticket. Redact.
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.
- Write the interface and the direction.
- Read the lines in order.
- Find any line that permits everything.
- Find a line that can never match.
- Delete those from the draft you will keep.
- Do not apply it on this page.
Mistakes that outlive the command
Access Control Lists (ACLs) Explained goes wrong in a small set of ways. The list is here so the ticket can forbid them before the window.
- A permit any left in place.
- Direction ignored.
- The list applied toward your only session.
- A shadowed line trusted.
- Addresses from a log pasted widely.
Decisions to write down
One decision for Access Control Lists (ACLs) Explained: Order was read. Any-any is gone from the draft. Direction is written. Nothing was applied. And logs are redacted.
Checks before you call it done
Confirm this before you call the change done: Interface and direction are in the ticket. The first-match example is written. No any-any remains. No list was applied. And a second session is part of the later lab. If one of those fails, stop.
First match wins.
Delete a permit of any to any.Before you leave the device
Access Control Lists (ACLs) 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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