# Rebooting the modem: Is it really necessary to leave it unplugged for 30 seconds? **URL:** \ **Category:** Factual Questions\ **Created:** [June 24, 2016, 3:29pm UTC](https://boards.straightdope.com/t/rebooting-the-modem-is-it-really-necessary-to-leave-it-unplugged-for-30-seconds/758241 "2016-06-24T15:29:12Z")\ **Posts on this page:** 8\ **Page:** 2
**Author:** ![BigT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bigt/32/12044_2.png) [@BigT](https://boards.straightdope.com/u/BigT)\ **Post date:** [June 26, 2016, 8:14am UTC](https://boards.straightdope.com/t/rebooting-the-modem-is-it-really-necessary-to-leave-it-unplugged-for-30-seconds/758241/21 "2016-06-26T08:14:35Z")
> [@Paxx](#): > > Thanks. That’s what I thought. > > Also, previously in this thread, you said:That’s what I’ve done over the years but I continue to be told by support techs to wait 30 seconds, which is interesting given this web page: [Why support tells you to wait 10 seconds before rebooting](http://lifehacker.com/why-support-tells-you-to-wait-10-seconds-before-rebooti-836539426). Interesting. I’ve always been told 10 seconds. And, BTW, I have actually had my modem act weird when I didn’t wait long enough. It wouldn’t actually boot and just showed the power light. But this was really fast, like less than a second–which isn’t easy since you always have to unplug them. I wonder if that’s why they don’t tend to have power buttons. ---
**Author:** ![nate](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nate/32/13085_2.png) [@nate](https://boards.straightdope.com/u/nate)\ **Post date:** [June 26, 2016, 3:28pm UTC](https://boards.straightdope.com/t/rebooting-the-modem-is-it-really-necessary-to-leave-it-unplugged-for-30-seconds/758241/22 "2016-06-26T15:28:54Z")
This is a WAG, but is it possible that the 30 sec wait is so that any device connected to that modem/router will likely time-out and have the reinitialize when connected again? ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [June 26, 2016, 6:32pm UTC](https://boards.straightdope.com/t/rebooting-the-modem-is-it-really-necessary-to-leave-it-unplugged-for-30-seconds/758241/23 "2016-06-26T18:32:18Z")
> [@nate](#): > > This is a WAG, but is it possible that the 30 sec wait is so that any device connected to that modem/router will likely time-out and have the reinitialize when connected again? Apparently some people aren’t getting it. There is no specific time. In some devices more than a very brief, less than a second drop in voltage is needed to reset it, and it varies by device, and per unit for the same device. There is no specific time needed, whether for the device itself or any interconnected devices. 10 seconds, 30 seconds, doesn’t matter, it has to be more than than just pulling the power plug out and then back in again the way people who push the elevator more than once will do it. If people are told 10, 20, or 30 seconds there’s a better chance they’ll do it long enough to work. ---
**Author:** ![septimus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/septimus/32/410_2.png) [@septimus](https://boards.straightdope.com/u/septimus)\ **Post date:** [June 26, 2016, 6:52pm UTC](https://boards.straightdope.com/t/rebooting-the-modem-is-it-really-necessary-to-leave-it-unplugged-for-30-seconds/758241/24 "2016-06-26T18:52:34Z")
How do excess charges (e.g. on capacitors) bleed out? Am I correct that it is often through very high (unpredictably high) resistive pathways? ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [June 26, 2016, 7:37pm UTC](https://boards.straightdope.com/t/rebooting-the-modem-is-it-really-necessary-to-leave-it-unplugged-for-30-seconds/758241/25 "2016-06-26T19:37:44Z")
I’ve owned computers where a legit 20 seconds was necessary (as indicated by numerous LEDs on the motherboard still lit after unplugging). Computers in their standby state are quite energy thrifty these days, and large power supplies have big smoothing capacitors. Even when the power is completely removed, DRAM [can retain (most of) its contents for several seconds at room temperature](http://citpsite.s3-website-us-east-1.amazonaws.com/oldsite-htdocs/pub/coldboot.pdf). This can lead to security holes and other issues. ---
**Author:** ![md2000](https://avatars.discourse-cdn.com/v4/letter/m/73ab20/32.png) [@md2000](https://boards.straightdope.com/u/md2000)\ **Post date:** [June 27, 2016, 12:44am UTC](https://boards.straightdope.com/t/rebooting-the-modem-is-it-really-necessary-to-leave-it-unplugged-for-30-seconds/758241/26 "2016-06-27T00:44:48Z")
> [@nate](#): > > This is a WAG, but is it possible that the 30 sec wait is so that any device connected to that modem/router will likely time-out and have the reinitialize when connected again? DHCP can be triggered (obtain new IP address) if your network connection on your PC drops for more than a few seconds (again, about 3 to 5). However, that’s only for PC’s or other devices plugged directly into your modem (assuming it’s the newer modem and router in one, with 4 ports). If your PC is plugged into a switch (that is plugged into the modem) or a separate router that never gets powered off, it won’t look for a new address or reset its network connection. > [@septimus](#): > > How do excess charges (e.g. on capacitors) bleed out? Am I correct that it is often through very high (unpredictably high) resistive pathways? No, through the usual path, more likely. But an RC circuit falls off with time (exponentially); and the capacitors, especially on the power supply smoothing, may be large and have a long time constant to smooth the voltage. So the capacitors may take a second or two to fall below the minimum of about 1.5V needed to ensure all transistors are off. If there are further capacitors in a complex circuit (like a PC) then the time may also be lengthened. 10 real seconds should be enough for anything. For some devices (like TVs) on-off does not fully power off the device, pulling the power may be necessary. They are still “alive” when off, and listening for that remote control. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [June 27, 2016, 2:05am UTC](https://boards.straightdope.com/t/rebooting-the-modem-is-it-really-necessary-to-leave-it-unplugged-for-30-seconds/758241/27 "2016-06-27T02:05:14Z")
> [@septimus](#): > > How do excess charges (e.g. on capacitors) bleed out? Am I correct that it is often through very high (unpredictably high) resistive pathways? Well, if the device is running, the charge will be used powering it. Which is essentially a very low resistance. ---
**Author:** ![gotpasswords](https://avatars.discourse-cdn.com/v4/letter/g/c57346/32.png) [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)\ **Post date:** [June 27, 2016, 3:37am UTC](https://boards.straightdope.com/t/rebooting-the-modem-is-it-really-necessary-to-leave-it-unplugged-for-30-seconds/758241/28 "2016-06-27T03:37:05Z")
Back when I had DSL and a Linksys router, one or the other of these devices could get hung up. IIRC, it was the router’s state table overfilling. I put both things on a digital lamp timer set to go on at 3:01 AM and off at 3:00, so they’d get an automatic daily 60-second shutdown while everyone in the house was sleeping. [Previous page](https://boards.straightdope.com/t/rebooting-the-modem-is-it-really-necessary-to-leave-it-unplugged-for-30-seconds/758241.md?page=1)