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 layer-4 balancer forwards a connection using the address and the port. A layer-7 balancer reads the HTTP host or the path and can send it to a different pool. The generators draft a config for a balancer you run. They do not sit in front of a service you do not operate.
Health checks should see the application, not only the TCP port, when a dead application still accepts the socket. Write the check. A certificate on a layer-7 listener is a secret you do not paste into the ticket.
One service. Adding a second site and a global balancer is a different design. Do not open the listener to the world if the service was meant for a named prefix.
An iRule or a snippet you do not understand is a snippet you delete.
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 service.
- Choose L4 or L7.
- Write the health check.
- Limit the source if the service is private.
- Remove secrets and unread snippets.
- Do not deploy in this hour.
Mistakes that outlive the command
Load Balancing Explained (L4 vs L7) goes wrong in a small set of ways. The list is here so the ticket can forbid them before the window.
- A balancer in front of a service you do not operate.
- A health check that only proves the port.
- A certificate in the note.
- An unread snippet kept.
- 0.0.0.0/0 on a private service.
Decisions to write down
One decision for Load Balancing Explained (L4 vs L7): The service is yours. The layer matches the need. The health check matches the application. Secrets are absent. And nothing was deployed.
Checks before you call it done
Confirm this before you call the change done: The service is named. L4 or L7 is written. The check is written. The source matches the audience. And the live balancer is unchanged. If one of those fails, stop.
| Layer | It can see | Choose it when |
|---|---|---|
| L4 | Address and port | The pool is one application |
| L7 | Host and path | One listener must split names |
Before you leave the device
Load Balancing Explained (L4 vs L7) 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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