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
Hosts in two VLANs talk when a device you administer routes between them. That device has one address in each VLAN, and the hosts use that address as their gateway. This page does not name a generator. The vendor how-to, later, is the command. This hour is the plan.
Write both VLAN ids, both prefixes, and the router. A prefix you were not assigned does not become a VLAN because the switch had spare ids. VLAN 1 stays the default you are leaving.
An ACL between the VLANs, if you need one, is a later ticket. Do not open every VLAN to every other VLAN in the plan and call it routing.
192.0.2.0/24, 198.51.100.0/24, 203.0.113.0/24, and 2001:db8::/32 stay in the note.
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 VLANs.
- Name both prefixes.
- Name the routing device.
- Write the two gateway addresses.
- Leave VLAN 1 as the default.
- Do not configure the device.
Mistakes that outlive the command
Inter-VLAN Routing goes wrong in a small set of ways. The list is here so the ticket can forbid them before the window.
- One gateway address used in both VLANs.
- VLAN 1 as the new user network.
- A prefix you do not hold.
- Every VLAN routed to every VLAN with no sentence.
- Configuring during the reading.
Decisions to write down
One decision for Inter-VLAN Routing: Two VLANs are named. Each has its own gateway. The device is yours. VLAN 1 is not the new network. And nothing was configured.
Checks before you call it done
Confirm this before you call the change done: Both VLAN ids are written. Both prefixes are written. Both gateways are written. No device was changed. And a later how-to is named or the work stops. If one of those fails, stop.
Before you leave the device
Inter-VLAN Routing 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.
Tools for this guide
This guide does not name a browser tool. The pillar it belongs to links the calculators for the neighbouring work.
Related pillar guides
More in this cluster
The pillar for this page, and the next published pages filed with it.