When Your Printer Goes Missing

Got a call from mom — her printer stopped working. Should be simple, right? Just SSH into her Zorin laptop (Sirius-Station at 10.42.0.174) and fix the CUPS drivers.

Famous last words.

What started as a printer issue turned into a full session: network archaeology, router reconfiguration, user account hardening, RustDesk reinstall, and a mystery TP-Link that's still out there somewhere.

The Printer Problem

My home network runs OPNsense at 10.42.0.1, with an ASUS RT-AX56U acting as the WiFi access point. A laptop connects via WiFi, and a Brother network printer should just... work.

CUPS showed the printer configured but jobs were stuck with "Unable to get printer status" and "The printer did not respond." Classic driver issue, I thought. Except the printer wasn't responding because it wasn't on the network at all.

Full nmap scan of 10.42.0.0/24 — no Brother printer (MAC 30:C9:AB:*). Not at its configured mDNS address, not anywhere.

Then I noticed something weird: the ASUS was advertising itself via mDNS as 192.168.0.108. But my network is 10.42.0.0/24. What?

Down the Rabbit Hole

WiFi scan from Sirius-Station showed all my ASUS SSIDs, but also... TP-Link_1D90.

I don't have a TP-Link router. Or do I?

Tracked it to MAC 14:EB:B6:13:XX:XX, getting strong signal from Sirius-Station's location. Running its own network at 192.168.0.1. This was getting weird.

The Subnet Problem

Sirius-Station was connected to the home WiFi and getting IP 10.42.0.174 from OPNsense just fine. But I couldn't reach the ASUS management interface — it was stuck on 192.168.0.108, a completely different subnet.

The Clever Trick

I needed to reach 192.168.0.108 from Sirius-Station without breaking the SSH session or internet connectivity:

# Add secondary IP — gives the interface TWO IPs simultaneously
ip addr add 192.168.0.50/24 dev wlx5ce931608890
# 10.42.0.174/24 — original (SSH still works)
# 192.168.0.50/24 — added (can now talk to 192.168.0.x)

# SSH tunnel from my desktop through Sirius-Station to the ASUS
ssh -L 8080:192.168.0.108:80 root@10.42.0.174

Opened http://localhost:8080 — boom, ASUS login page.

What Actually Happened

After the power surge, the ASUS booted before OPNsense came back online. DHCP timeout → fell back to its default static IP of 192.168.0.108. OPNsense eventually came up, but the ASUS already had its fallback IP and stuck with it.

WiFi kept working because it was bridging clients to 10.42.0.x just fine. Only the management interface was stranded on 192.168.0.x.

The Fix

Changed the ASUS LAN IP from 192.168.0.108 to 10.42.0.2 (static, not DHCP). Set gateway to 10.42.0.1, disabled its DHCP server since OPNsense handles that.

The printer is still stuck on 192.168.0.104 (old subnet) — needs a physical power cycle and reconfiguration to DHCP so it gets a proper 10.42.0.x address. That's a next-visit fix.

The Sirius-Station Overhaul

While I had SSH access, I addressed several other issues:

User Account Hardening

User user_primary was the only account with full sudo access including NOPASSWD. Root was locked. No other admin.

Created user commander with sudo access
Removed sudo from user_primary (kept as standard user: adm, cdrom, dip, plugdev, lpadmin, sambashare)
Deleted /etc/sudoers.d/user_primary (had user_primary ALL=(ALL) NOPASSWD: ALL)
Enabled root login with password
Added SSH keys (ed25519 + RSA) to commander and root

RustDesk Reinstall

RustDesk 1.4.0 was installed but connection failing — config mismatch between machines (Sirius-Station pointed at remote.lab.internal, local was on rs-ny.rustdesk.com).

Uninstalled 1.4.0, removed all configs
Installed 1.4.5 (latest) via apt
Configured for remote.lab.internal server

Printer Drivers Installed

Even though the printer isn't on the right subnet yet:

hll3290cdwpdrv:i386 (1.0.2-0) — Brother proprietary
printer-driver-brlaser (6-3) — Open source
brscan4 + brscan-skey — Scanner drivers

Pending Items

Power cycle Brother printer → set to DHCP → get 10.42.0.x address
Reconfigure CUPS with new printer IP
Find that mystery TP-Link physically and decide its fate
Zorin 17 → 18 upgrade (official upgrade in early testing)
Consider putting IoT/printer on separate VLAN

Lessons Learned

Secondary IPs on a single interface are incredibly useful for reaching misconfigured devices
Power surge + boot order can cause weird fallback behavior — always set static IPs on infrastructure devices
mDNS announcements can be stale/misleading
Single admin account with NOPASSWD sudo is a security risk — always have a separate admin user
Sometimes the "simple printer problem" turns into network archaeology

The printer? Still not back yet. But the network topology makes sense again, the ASUS has a proper IP, user accounts are hardened, and RustDesk works. I'll call it progress.

When Your Printer Goes Missing: Network Archaeology and a Sirius-Station Overhaul