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 prefix-list names the prefixes you will accept or announce. An AS-path filter names a pattern of AS numbers. The tester and the generator draft text. They do not open BGP and they do not advertise.
A permit that matches every prefix is a line you delete. You announce only what you were assigned. You do not accept the full table into a lab note as if you had agreed to it. One list.
Apply nothing during the reading. A live session you do not administer is out of scope. Documentation prefixes are the example.
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 prefixes you originate.
- Draft one list.
- Delete a permit of any.
- Read the AS-path pattern if you use one.
- Do not apply it.
- Do not open a session.
Mistakes that outlive the command
BGP AS-Path Filtering and Prefix-Lists 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 the list.
- Advertising a prefix you do not hold.
- Applying the draft to a live session.
- A new BGP neighbor.
- A pattern you did not read.
Decisions to write down
One decision for BGP AS-Path Filtering and Prefix-Lists: The prefixes are yours. Permit any is gone. Nothing was applied. No session was opened. And one list is the scope.
Checks before you call it done
Confirm this before you call the change done: The list is written. The wide permit is gone. The session name, if any, is yours. No neighbor was added. And no route was advertised. If one of those fails, stop.
# Draft only. Do not apply.
# Delete a permit of every prefix.
# Announce only what you were assigned.
# 192.0.2.0/24 is documentation.Before you leave the device
BGP AS-Path Filtering and Prefix-Lists 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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