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
RFC 2317 is a way to delegate reverse DNS for a prefix longer than a /24 by using CNAMEs in the parent reverse zone. The generators draft the names. They do not change DNS and they do not send a zone transfer.
You need the parent reverse zone, or a provider who will add the CNAMEs, and the child zone you will serve. If you hold neither, stop. 192.0.2.0/24 is documentation. A transfer of someone else's zone is not a step.
One prefix. Write the parent, the child, and who will type the CNAMEs. Do not install the zone during the reading.
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 prefix you administer.
- Name the parent reverse zone.
- Draft the CNAME names.
- Keep the child zone as a draft.
- Do not transfer a zone you do not hold.
- Do not install it yet.
Mistakes that outlive the command
Reverse DNS Delegation for Subnets (RFC 2317) goes wrong in a small set of ways. The list is here so the ticket can forbid them before the window.
- A delegation for a prefix you do not hold.
- An AXFR of a foreign zone.
- A documentation prefix filed as production.
- Installing during the reading.
- CNAMEs pointed at a name you do not control.
Decisions to write down
One decision for Reverse DNS Delegation for Subnets (RFC 2317): The prefix is yours. The parent owner is named. No foreign transfer. Nothing was installed. And one prefix is the scope.
Checks before you call it done
Confirm this before you call the change done: The prefix is written. The parent zone is written. The child name is written. No transfer was requested. And no zone was edited. If one of those fails, stop.
Before you leave the device
Reverse DNS Delegation for Subnets (RFC 2317) 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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