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
When two protocols offer the same prefix, administrative distance picks the source the router prefers. The reference lists common defaults. Your platform's table wins over memory. The page does not configure a router.
A lower distance is more trusted on the platforms that use this number. Changing it so a worse route wins is a choice you write in a sentence. Do not change it during the reading.
One prefix you administer. A floating static is a backup with a worse distance, and it is still a later change.
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 two sources.
- Read the default distances.
- Write which one should win and why.
- Do not change a distance.
- Do not install a route.
- Stop.
Mistakes that outlive the command
Administrative Distance Explained goes wrong in a small set of ways. The list is here so the ticket can forbid them before the window.
- A distance changed so an accidental route wins.
- Trusting a memorized table over the platform.
- Two prefixes in one note.
- Installing the route during the reading.
Decisions to write down
One decision for Administrative Distance Explained: Both sources are named. The platform's numbers were checked. The winner has a reason. Nothing was changed. And one prefix is the scope.
Checks before you call it done
Confirm this before you call the change done: The prefix is written. Both distances are written. The reason is one sentence. No router was changed. And no route was installed. If one of those fails, stop.
Before you leave the device
Administrative Distance 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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