Responsibility of the Network

Good Morning from my Robotics Lab! This is Shadow_8472, and today I have a doozy of a network week to cover. Let’s get started!

Meet the Computers

  • Cerberus – the main star today. It is our new hardware firewall running OPNsense
  • Red Router – a tp-link gaming Wi-Fi router fancied up beyond what it should have been
  • LAB – my homelab with a few servers
  • LAN – everything else connected via Wi-Fi or Ethernet

Network Implosion

It all started with revisiting a .lan domain. Cerberus’ extensive webUI left me with the hunch I’d need one machine in charge of DHCP assigning dynamic IP addresses. Red Router’s “operation mode” to work as an access point was hidden in literally the last menu to click through.

It was afternoon and no one would be using the network for the 30 seconds to 5 minutes I estimated switching the LAB and LAN Ethernet cables from Red Router over to Cerberus would take. Nope. No traffic made it through. DHCP mis-configuration? Cue a slow back and forth, bopping a setting from a workstation and trying a different physical configuration. Eventually, Cerberus ended up on my desk with Red Router talking directly to our ISP’s gateway/modem.

Order of events is a bit fuzzy from here, but when the Wi-Fi stopped working, I was without a good access to online answers. I worked the problem into the night. Around 1:00 AM, I knew I had done too much for a clean reversion. For two hours, I worked in loops hoping to spot something different. So much waiting! Cerberus would behave on my desk, then fail when redeployed. Worse: when I re-connected all the wires to Red Router, it started dancing between 192.168.0.1 and 192.168.1.1 every 45 seconds or so. I configured its IP manually, but gave up on Internet by morning at 3:00 AM, preparing to concede to my father’s suggestion earlier about hiring a professional to untangle my mess.

The Next Day

Newtork Loop. In my brain fog, I had Red Router talking to itself on a cable leftover from removing Cerberus for the night. With the house to myself for several hours, I alternated between bursts of intense diagnostics and mental processing. Somewhere in there, I rebooted the ISP’s modem.

Around noon, I realized the extra ports on Cerberus aren’t a switch as is Red Router’s default configuration, but were following firewall rules – which explained its behavior the previous day when I tried a computer from LAB without anything in-between. At around 3 PM, I got a Discord notification while mentally checked out, letting me know the network was back on.

6 PM on the second day: I situated my workstation in Cerberus’ LAN port and a Raspberry Pi in one I named LAN2. I’d previously copied firewall rules from LAN to LAN2 and LAB, but to no obvious effect – until I had the two computers ping each other. LAN2 failed as expected, but LAN’s ping was returned. I corrected the interfaces’ rules to allow them to reach out, and that was it.

Fallout

Without going into too much detail, a subnet shift like this is a major undertaking for networks with static IP servers on them. Not only do the network and computers need to be adjusted, but all traces of the old subnet need to be corrected. NFS clients needed to be told where the server was now, and the NFS server shares needed to be updated about what IP’s were allowed to mount them. I also still have Bitwarden to clients to update at my leisure.

Takeaway

OPNsense is a heavy weight in terms of configuration options. It has a learning curve compared to products simple enough to for Grandma and Grandpa to use. I may have solved my own emergency, but it may be wise to get someone looking at it professionally anyway to grade my work and give me some pointers on rootless Podman mounting NFS shares, or other long-term places where I’ve gotten stuck.

Final Question

I admit: networking is more fun than I gave it credit for before I knew basically anything. I still find it a bit taxing to mentally reach around my mental map, but I manage. How do you visualize networks?