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System Redundancy (feddit.uk)
submitted 5 months ago by Cyber@feddit.uk to c/selfhosted@lemmy.world
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After being home for weeks, I went away for business, the 1st night away there was a brief powercut and the firewall (on a UPS) seemed to get stuck.

So, that's no DNS, DHCP, or connectivity between wifi and LAN... All due to (admittedly aging) hardware issue.

Since then my entire home system has had issues whilst it all settles down.

It made me think about getting some redundancy into the system to handle a single failure.

So,.can you give me any insights into High Availability like CARP (for pfSense), VM failover (on Incus?), mesh wifi, Home Assistant, etc?

Of course there are going to be single points, like ISP line, etc, but seems like something to test out.

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[-] Cyber@feddit.uk 3 points 5 months ago

Good points there.

For 1. The ISP router is a Fritz one set to bridge mode running over a PoE adapter from the same UPS the firewall is using. It stayed up all the time (looking back at the logs)

  1. Not sure what happened here, but the firewall is the DNS resolver and when everything else powered back up, nothing got an IP address. Now, whether thw service failed or the WAPs took longer to start than the devices could wait, I'm not sure, but as Scotty said: it's dead Jim.

  2. Good point. I don't need it ALL to be redundant.

  3. Also good. The UPS is directly connected to the firewall (which has NUT in), but it doesn't inform anything else... I'll look into that too.

Nice mental reset for me about over thinking it... thanks

[-] just_another_person@lemmy.world 2 points 5 months ago
  1. Okay, so no issues there
  2. DHCP handles the address assignments in your network, not DNS. DNS resolves to named host queries. If no devices got IP addresses, that's one problem. If you couldn't resolve public hosts like www.news.com, that's a DNS problem. If you couldn't resolve INTERNAL named hosts you refer to around your network, then that's also DNS, but a different problem.

My hunch here is that you MIGHT be using a named host as your DNS resolves instead of an IP address in your network, OR, for some reason your DNS resolves doesn't have a static address. Never use named hosts to point to network services, and all network services need a static IP, so go and check all of that.

[-] Cyber@feddit.uk 2 points 5 months ago

Yep, all good with DHCP vs DNS.. just my grammer was terrible.

Nothing was getting an IP from the DHCP, when the wifi returned...and... DNS was also not working for the few devices that still had an IP.

Sry bout the confusion there.

[-] just_another_person@lemmy.world 3 points 5 months ago* (last edited 5 months ago)

So then as a next step, I'd set Wireshark up on one of your regularly hosts, set it to filter for DHCP traffic, confirm you're seeing regularly advertisements first, then reboot the device that's responsible for DHCP and make sure it resumes sending those advertisements when it comes back.

If it's the same device handling DNS, make sure it's also immediately returning responses after the reboot as well with dig or nslookup.

this post was submitted on 31 Jan 2026
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