Secondary/backup router, best way to go?

Hardware
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Hi. I have a problem with my ISP’s router: it reboots several times a day, usually in the hottest hours of the day, but sometimes also at night.
I don’t want to change ISP because it’s the only one to offer optical fiber from home, in my city, but unfortunately I’m forced to use their router. I’ve read several people complaining about the reboots, and already tried to cool the router with the most powerful fan I have found of compatible size, but with no luck (5/10° less then before, still rebooting apparently at random).
I have a 4G backup connection for my PC, but my “smart” devices go offline for about 5 minutes at every reboot, while the WiFi is available again.

Last week I made my first installation of Hassio on an RPi3 with Conbee2, and I already fell in love with it. Now I can control various devices from their native clouds and also from HA (but I’ll take the “next step”, detaching from clouds, as soon as i’ve time to reconfigure everything) and I still have the reboot problem: as static ips are assigned by the router, HA goes offline with it too.

The ideal solution for me would be to have a device that provides a WiFi LAN while the router is rebooting, and assigns the same IP addresses (I could scrape IPs and MACs daily from the router’s web interface to keep it updated, but it’s http so… not sure, maybe i’ll just set them manually on each “router”).
I’ld prefer not to always have a DHCP server and routing tables not the main router, to keep latency down: speed is a concern, and when the router is powered it’s great.
If this secondary device could also use the 4G hotspot to provide a backup LAN with internet, that would be great, as I could still connect to HA via WireGuard when not at home. But i’ve not figured out how to implement it yet.
I’d already be equipped to create a fake access point of my own WiFi, but I don’t know if it’s a good idea.

Another solution I thought of is to permanently separate hassio-connected devices from the rest of the LAN, via a dedicated subnet or WiFi. So the secondary router (not necessarily a “router”: it could be another RPi, or the same one in which Hassio runs, or … I don’t know, suggestions are welcome!) would always be active, and it could use 4G too to provide me access to Hassio, whether I’m at home or away, when the main router is down.

Here’s how the two network maps would look like:

map3
map3960×540 74 KB

Any idea? Thank you so much in advance for the feedbacks, and for all the information this magnificent community has already given me.

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You could probably add a second router.
If this router is connected from your existing router LAN port to INTERNET of the new, then the new router will be a new DHCP router.

That should mean the first router just forwards the internet to your new, and the new one has all the devices connected to it.
When the first router reboots the second will only notice that internet is down but all devices are still connected in the second network.

The important thing is that you move all devices to the second router.
I have never tried this setup but it should work.

Are you sure you can’t use any router you want?
Most of the time ISPs want you to use one router but there is nothing hindering you from switching.

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I would use something like an ubiquiti edgerouter X, or any more expensive version of that series. On that you can setup both your ISP’s connection (through your current router) and the 4G connection as a backup connection. So no more downtime. From your story I got the impression that you think another DHCP server on a device like this causes more latency, while that is true in a way, it is about 10ms max, so you wouldn’t notice it. This is about the same route @Hellis81 explained above.

And sorry to disappoint you, both schema’s you propose are not going to work. Routers aren’t made to work like that. And you make it harder then it is.

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Yeah, this is very good option. What I’d add is to use dual-WAN router with support for USB 4G modem (one of options). I use Draytek Vigor 2925 in such configuration. \Pretty dumb router from my ISP is configured in ‘bridge’ mode and connected to WAN 1, USB 4G dongle is connected to USB port of my router. Then if there is outage on ISP side Draytek kicks off fallback connection to cellular network via modem. This way not only LAN side is always on, but also interruptions in internet access are minimized.

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I’d always recommend splitting your devices into basic building blocks rather than relying on all-in-one devices, and referring to them as such to avoid confusion. This gives maximum flexibility, upgrade paths and ability to troubleshoot / replace separate components as required.

As already suggested (including by you), what you want to do is to turn your ISP’s box into a modem (the bridge mode you refer to), so it’s not a router at all, just a modem (or gateway + modem).

Your router connects to that, then you have your switch(es) and wireless access point(s), which may be in the same box.

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Hay bro only read your bit

your ISP dont care what router you have as long its sucking the internet down

I had the same problem router rebooting thing not joining the network wifi … it was f… me off

someone said try pfsense did some youtubing found my self a pc 6gb 500gb hard drive $80

put pfsense on it and it did work bugger

phone help desk ask why router not working with out telling them I change router can they help
plug old one in prayed they got to change the vlan (dont didnt know what that was) he said should be 10
remember see vlans in the menu Interfaces/ VLANs jump there made one with 10 attach it the wan

and shit I can see the google HAPPY HAPPY CAMPER hung up (nicely)

made pfsense same ip address as old router

turn old router into access point only

48hours no reboots happy camper wifi still problem
started looking for something

found nuifi mmmmm cost $$$$

them I found tenda access point manual not in english
but only $90 to get to my place nuifi $180 to get to my place (well could be a good weekend project again)

week before lockdown all the bits a day to setup up a day testing it went live
wife come home says im working form home sh…t

well im home to have old router just in case with heaps of rebooting

well 30+ days on line NO reboots

found pfBlockerNG install that house see no ads

me happy camper even happyer for just wing it LOL

just up graded to 2.4.5 7 days with no reboots

hope this help

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Thanks a lot everyone for your replies!

@Hellis81 : I’ve already tried changing the router but couldn’t get it online. I also don’t know the details of the communications between the ISP and their router, so I’m afraid they’ll notice and close the contract (using their router is mandatory).

@frits1980 : ubiquiti edgerouter X doesn’t have WiFi capabilities, right? Could you please explain why my schemas won’t work?
Also, having more then a dozen devices with static IPs plus a few more IoT stuff connected, i’m afraid latency would be higher then 10ms if i use something like a RPi. Probably it won’t be a problem if i just use a dedicated router.

@ mirekmal : the Vigor 2925 seems optimal for my needs, but i can’t find it for less then 400€, which is a bit too expensive. Also, i don’t have a USB 4G dongle, it’s just a secondary phone that i always leave at home with hotspot enabled, and is set as 3rd connection option on my other devices (right after 5Ghz and 2.4Ghz WiFi from my main router).

@ Troon : i totally get your point and agree with it as a general rule. On the other hand, having too many devices to achieve a connection increases the risk of going offline due to a failure on a single link in the chain (missing updates, changes to configurations or who knows what else). I’ld prefer to keep it as simple as possibile. So having my ISP’s modem + max another device for routing/AP, as you too suggested, would be my preferred path.

@ myle : ISPs here are uncomfortably picky about letting clients use their own routers. With other ISPs i managed to use mine, but not with this one, and I’ld keep the contract active because they offer the best connection in town. Can’t find any info on “nuifi”, did you mean unifi maybe?

(sorry for not tagging everyone, but as i’m a new user i can only add 2 tags).

Summarizing, from what I understand the best solution is to use a second device with router functionality, connected to the ISP’s router/modem via ethernet, and to my 4G hotspot via WiFi. Then disable DHCP on my ISP’s router, and its WiFi broadcast, so that it only serves as a modem to my second router.
Do you have any suggestions for a device with internet access capability both via ethernet and through connection to a 4g wifi hotspot, with a 100/200€ budget max?

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That part right there is what I believe is not possible.
I have never heard of it, and it make no sense to build such a device.
If you already have wifi, why share it to the router that then needs to share it to all other devices?

It will mean there has to be two wifi chips, one for receiving and one for transmitting, in a router, that has a sole purpose of transmitting internet.
Maybe I’m wrong. But I have serious doubts about that part.

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I know it’s not a common scenario, that’s why i was thinking about setting up a second RPi with an Alfa AWUS036NHA to act as a backup WiFi LAN, instead of a real router.

It’s just my current setup: i’ve to have a second phone for work, so i might as well use it to share its connection with my LAN when the ISP’s router is down, but i surely don’t want to use that phone as DHCP server/router…

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This one I don’t understand. DHCP is only used when first obtaining a IP-address. Once a device has an IP-address, it is no longer a concern ?

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You’re right @francisp , I explained myself badly: the secondary device should also have routing tables, as well as function as a DHCP server, otherwise when the main router is offline i’ld still have the problem of not being able to control smart devices.

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And this is why I said your schema’s don’t work. 2 DHCP server on 1 network only work if they use 2 distinct IP scopes. But since you are referring to the second one as a backup for the first it will not work. There is no such software (or hardware) which provides a fallback DHCP server.

So the only route to go is:

Where you can use any brand/model router instead of the Vigor (as long as it provides dual WAN) And the reason I suggested the Edgerouter X is because of it’s pricepoint. It does not provide Wifi. But like @Troon already said I wouldn’t want Wifi in my router, just because I like to place my AP('s) on a different spot then my router.

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Oh, i see @frits1980. I surely won’t have two DHCP servers on 1 network, that’s why i was thinking about a secondary device that only enables itself when the main router is down, OR a subnet/second LAN for my IoT devices.

I don’t have a secondary ADSL line, and i’m not sure i could get one. Also i won’t be happy to pay 25/30€ per month to another ISP, when i already have a backup 4G connection.

Still, thanks a lot for your feedbacks and scheme!

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In my example:
ADSL = 4G = Cable = Fiberglass = WAN = Internet

It’s not about what type of connection you have, it’s about the fact you want to use one as a fallback for the other.

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Ok, I get your point. Now I just need to figure out the right device for the job, just like the Vigor2920 in your scheme, but preferably cheaper.

Do you see any advantage (or disadvantage) in having a dedicated LAN for the IoT stuff instead?

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A dedicated LAN is not a bad idea. But it could also be a VLAN. I think the best thing you can do is search a router (with or without WiFi) which fits your budget and supports dual WAN.

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You could also solve this with a switch (not router) and a WiFi access point. Wire the switch to the ISP’s router, and wire the AP to the switch. Then, if/when your router goes down, the switch and access point will be able to handle all traffic on your WLAN without the need for your router. WiFi stays up, traffic sees no dip, and local network access is uninterrupted. All IPs stay the same, all DHCP etc. is all still managed by your ISP’s router.

You can use an old router as a switch, or any cheap router that can be flashed with DD-WRT or another 3rd party firmware. Alternatively, you can use an actual switch (I’ve got a 16 port PoE switch that’s powering my AP), but those can be pricey depending on features. Used enterprise grade network gear can be found cheaper (but still not cheap) on eBay.

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Although it might work, if one of the devices decides to release it’s IP or reboot your screwed. So I wouldn’t recommend it.

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Availability of devices might depend on the country your living.

My router has a WAN port to use an external modem and supports USB modems, especially USB tethering via Android phones.
It is a german brand ans also very popular here but I think not available in each and every country.

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@ptrsnja i’ve a TPLink Range Extender and a “HooToo TripMate Nano”, both with DD-WRT on it, which may do the job. I just need to check if I can configure one of them as an extender/second router when the main WiFi is up, but connect to my 4G and serve as a DHCP server and router when my ISP’s device is rebooting.
As @frits1980 pointed out, i still need DHCP & router, many IoT devices are unreliable and will disconnect a lot of times.
Maybe a simple shell script in cron, switching between different config files and rebooting services, will do the trick.