need to power cycle modem remotely

Consider changing you router for a more reliable one. Consider changing your ISP for a more reliable one. Power your router from a cheap time-switch that power cycles it at 3am whether it's needed or not.

USB operated relays are readily available, and they handle mains.

Or use one of the SONOFF switches - see eBay - that work from an app (can be hacked to have a webserver instead).

time switch wifi socket

Presumably the need to reboot the modem is because the internet connection is up the spout when Bill wants to view his CCTV from afar? So something that can reboot the modem e.g. via SMS would be more helpful?

Why?

If it's fallen over and lost the link you won't be able to remotely do anything.

If a bad line or noise has knocked the speed down ADSL2+ recovers quite quickly on it's own (unlike ADSL which can take up to 72 hours).

If the modem and/or DSLAM has got it's knickers in a twist over the required signal to noise level a reboot won't affect that. You need to start the 10 day training period, this instruction has to come from your ISP most like as a result of you calling/emailing support or via a webpage on your account details.

The last is the only one that occurs here. The modem stays up until either there is a power cut long enough for the UPS to flatten it's batteries or I switch it off to do "maintenance".

Personally I'd VPN into the home network and access the devices web interface over that to restart the link or reboot the device. Then sit nervously waiting for it to come back up...

Get into the admin screen remotely and reset from there. All my routers/modems have had reset option in the admin menus.

Examples

Stick a Raspberry Pi with a relay onto the network. Ping an outside address once every minute and if nothing is returned for 5 consecutive minutes, use the relay to power cycle the modem/router.

SteveW

Bill Wright expressed precisely :

A modem with OpenWRT installed as the firmware, will allow the router to be set to reboot as frequently as you like - hourly, daily, weekly, or at set times and several times a day.

mains switched outlet controlled by mobile phone? Brian

Nothing to stop him having two routers though one for the normal stuff and one that can be power cycled on over the web from a phone. I'm sure I've seen this done. Brian

long piece of string?

With built-in "deathdapter" [TM]BigClive

These look safer, but stupidly priced.

Do you need to reboot at will, or are you finding that long periods without use lead to something "jamming up" ?

I had the latter problem with a WiFi HP scanner/printer - it really didn't like being left alone for long periods, and went into a "power save" mode, which anecdata from the internet suggested was code for "off".

Rather than dick about trawling loads of half-posts everywhere (most of which suggested it wasn't fixable) I just put a mechanical segment timer on it, and it power cycles around 3am every day.

Been fine for a few months now.

These wireless doo-dahs are all very well, but I have to admit, I'm loath to trust them.

That is a good answer. Heartbeats are a reliable technique to ensure server availability.

The thing that wasn't obvious to me is the relay mains switch, easy to wire it up, but I don't know how to enclose it safely. I can do a home made box and sticky tape but is there anything more professional?

Even the ready made wifi devices like Sonoff are not something I would want lying around, in the open, if they were using main power.

Just for you, here's a clarification: F*ck off.

Bill

How do I know which is more reliable? How do I know the problem is with the router?

How do I know which is more reliable? How do I know the problem is with the ISP?

That would work, but ideally I need to power cycle it as soon as it stops working.

Bill

That looks very promising.

Bill

Every time you re-boot your modem it has to go through the re-training. There must be a reason for failing. I had an issue for many years and eventually tied it down to the Draytek router was randomly dropping my main ZEN connection and switching to Plusnet on failover. Took a re-boot to get Zen back up again. Only found out that the router was the cause when I plugged an old, suspected to be faulty router in while waiting for a replacement to arrive and everything just worked. Nothing's fallen over or needed re-booting for a good 6 months now.

I'd replace modem first as they're cheap as chips and then replace router if you still have issues. Always good to have a spare router pre-configured for hot-swap diagnostics.