Every network engineer has one story that begins 'I only changed one line...' The professional difference is that their story ends with a restore, not a rebuild. This is the classic TFTP job, done properly: back up the running configuration before the change, and know exactly how it comes back.
Of everything TFTP is used for, this is the job it was born to do and the one the video series is built around. A managed switch keeps its entire setup in a text configuration, and its own copy commands speak TFTP natively. The backup takes under two minutes, produces a file you can read with your own eyes, and turns any future disaster — failed change, dead hardware, factory reset — into a restore instead of a reconstruction from memory. The commands below are the documented ones for Cisco IOS-class switches; other brands offer the same copy idea from their own menus, pointed at the same TFTP server.
A switch lives with two configurations. The running-config is what it is doing right now, in memory — including the change you made five minutes ago that nobody saved. The startup-config is what it will load after a reboot, stored in NVRAM. Back up the running-config before a change: it is the true current state. And if the running state is good and intended to survive reboots, save it deliberately with copy running-config startup-config — a separate act from backing it up to your PC.
Thirty seconds of preparation prevents the two classic fumbles:
192.168.1.10device-purpose-date.cfg, like switch-core-config-2026-10-25.cfg — this name gets typed on the switch and must match what you expect to findcopy running-config tftp:Open the backup in a text editor before you touch the switch. You should see the hostname, interface settings, VLANs and the rest of your network in plain text. This ten-second check catches the embarrassing failures — the empty file, the old file from last month with today's name typed wrong, the transfer that actually failed quietly. A backup you have not looked at is a hope, not a backup.
The day this file earns its keep, the route back is the same road in reverse:
copy tftp: running-config, giving the server address and the exact file namecopy running-config startup-configHonest note: a merge is not a time machine. Settings present now but absent in the backup can survive the merge, so for a full return to a known state, experienced engineers reload the device with the restored file as its startup config. Either way, you are recovering from a file — not from memory.
The backup that saves you is the one taken before the change, as a reflex: before firmware upgrades, before 'small' VLAN edits, before anything typed after the words "quick fix". Date-named files cost nothing and stack up into a history you can diff when a mystery problem appears — 'what changed?' is answered by comparing two text files instead of by guessing. Move the files out of the TFTP root into your real backup location the same day, as covered in the root-folder guide.
copy running-config tftp: before the change and a restore route after it — that gap is the entire difference between an incident and an anecdote.
The full TFTP server setup — installation, root folder, firewall and a live transfer — is shown step by step in the video.
▶️ Watch Full VideoFrom privileged mode: copy running-config tftp: — then answer the two prompts with the TFTP server's IP address and your chosen destination file name. The switch shows exclamation marks as blocks transfer and reports the byte count when done. Confirm on the PC side that the file arrived in the server's root folder.
Back up the running-config — it is the live state of the switch, including recent changes. The startup-config can be older than reality if changes were never saved. For a complete safety net, some engineers take both, but if you take only one, the running configuration is the truth of what the network is doing now.
Check in this order: the TFTP tool's log (did the request arrive and complete, or error?), the root folder the tool is actually using (not the folder you think it is using), and whether you are looking for the exact file name you typed at the switch prompt. A 0-byte or missing file with a 'successful' switch message usually means the write side on the PC failed — folder permission is the prime suspect.