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
Echo, unreachable, time exceeded, and fragmentation needed are the types most tickets mean. The lookup names a type and code you type. It does not send ICMP. A time-exceeded message is how traceroute is often built. It is not a license to map a network you do not administer.
One type from a capture or a log you may hold. Write what it usually means, and that a filter may have dropped the message you expected. Do not sweep addresses to see who answers.
The next step is a sentence about the path you administer.
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 type and code you saw.
- Read the name.
- Write the path it belongs to.
- Do not send ICMP at a range.
- Do not map a foreign network.
- Stop.
Mistakes that outlive the command
ICMP Types and Codes Explained goes wrong in a small set of ways. The list is here so the ticket can forbid them before the window.
- A sweep of addresses.
- Traceroute against a network you do not administer.
- A missing ICMP message called proof without the filter checked.
- Sending the type as a probe.
Decisions to write down
One decision for ICMP Types and Codes Explained: The type came from a log you may hold. The name is written. No sweep was sent. The path is yours or the log's. And no foreign map was made.
Checks before you call it done
Confirm this before you call the change done: Type and code are written. The name is written. The path is written. No probe was sent. And no range was scanned. If one of those fails, stop.
Before you leave the device
ICMP Types and Codes 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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