When you reset the wi-fi router, why does it take so long to turn on? What happens during that time?


When you reset the wi-fi router, why does it take so long to turn on? What happens during that time?

In: Technology

Routers are mini-computers that also can send and receive wifi.

The router has to turn on and boot up, just like any other computer.

The router itself is basically a mini computer. Just like the computer you use, it has a CPU, memory, storage, an operating system (the “firmware”), etc. All of these are of course specialized for its job of handling network traffic.

And just like your computer, it needs time to start up after it’s been turned off. During that time it does the same sorts of things your computer does when it boots – initializing its hardware, loading the operating system, and launching various software components that allow it to do its job.

The hardware on routers is usually quite weak, since they only need to be good enough to perform the one job they are designed for. They run much slower than your computer. So, even though a router is a comparatively simpler device, it may take longer to start up than your computer.

Your router has several hardware components.

* Integrated switch (physical network connections)
* Wireless RF circuitry for sending and receiving data
* Processor and routing software to handle data-link stuff
* NVRAM – non-volatile memory – stores configuration information and system software
* RAM – stores currently running configuration and copy of system software

The router will run a self-test on its hardware when starting up. During this period, it will give out fault codes and other diagnostic information if the system has internal data corruption or other hardware errors. This takes up time. Fun fact – you can actually connect a serial line directly to the board on most routers and observe this in a console.

So the memory copy rates aren’t all that fast when a router boots up either. This is why, for instance, it still takes a good minute or two to update the firmware after you have downloaded it. After boot, It will copy your firmware / operating system and configuration from NVRAM to RAM. This takes up a good deal of time.

Once the hardware tests are passed and the router’s software is loaded up, each piece of hardware gets “initialized”. This is the part where the router looks at your connected devices and establishes connections. Things that are wired into the switch (such as a modem or gateway), checking the current bands and selecting the least congested one, and bringing any other software on the router up (such as a VPN service).

There is a lot more going on under the hood than listed here, but this is ELI5 after all.

EDITS: Just fixed a couple typos. I also see lots of people making a valid point that this isn’t “ELI5”. Also that a router is “just a small computer”. The thing is, it isn’t just like a small desktop/laptop. It has very specific hardware and software that accomplishes a very specific set of tasks. Unfortunately, this question can’t really be meaningfully answered in the framework of ELI5. A 5 year old would just have to accept that it needs time to start everything up and get everything talking to each other.

When the router comes on it has to contact many government agencies to make sure it’s okay that you have the internet back and that they are still able to listen and record everything you are doing on the internet.

I can answer this, because I work with routers.

Turning a router on and off is similar to turning a light on and off a light build. It should turn on instantaneously. Which it does.

But for a router to work, it needs to run programs or software that communicates back to a station. That software is what’s causing the router from working straight away. It will send out a command which identifies itself to a station, wait until the station respond, then proceed to continue run everything else which can take some time for the router to process.

Boot up time is also depended on it’s hardware. So faster chip means faster computation that process the software quicker.

Just one thing I’d like to add to all the (otherwise great!) answers: the “WiFi router” you’re talking about is probably a 4-in-1 device: it’s a WiFi *access point* (sends out and receives the WiFi signals, obviously); most often also a *switch* interconnecting several Ethernet ports and the WiFi access point; a *router*, which decides whether to send a packet from your ISP to your WiFi and vice-versa; ans finally, most crucially, a modem which allows it to connect to your ISP. Now in most cases, the slow part is just that last one: access points, switches and (to a lesser extent) routers are often rather simple devices that boot up quite quickly. A modem however, needs to make a connection over miles and miles of cabling, authenticate that connection with your ISP etc. It’s quite a bit more specialised, hence why it all takes a bit longer.


One point that people here are missing, is that most routers have a boot wait period.

At poweron the thing waits anywhere between 1 – 20 seconds, doing nothing, to see if you’re trying to debug or update the firmware.

Your router is waking up like a nonmorning person- its hair is a mess and it’s slow to get moving. So it needs to go to the mirror and see that its hair is a mess then take the time to fix it. Once its hair is fixed and teeth are brushed, it goes out and says goodmorning to the family- Mama Modem and Daddy Desktop, along with any other siblings it may have. Mama has prepared breakfast as always and its your router’s job to set the table and pass out the food to everyone. And as much as we all wish food instantaneously appeared on everyone’s plates, it takes a little time.

Routers have several components, both hardware and software (physical parts and programs). Your router will check itself for issues when you turn it on. You can watch this process with the right tools! Once the check is passed, it pings the things that its connected to, such as your modem and computer, and tries to connect to them, looking to take internet from the modem and give it to anything else plugged in (such as computer, gaming consoles, etc).

Answer: Routers are small specialized computers, just like computers they have to perform test to ensure the hardware is good. They will then boot up the operating system and find your last configurations and boot them too. For this reason is why they take a bit of time to boot up.

Most people in this thread seem to think that just because a router is a “mini-computer” it obviously means that all answers to all problems has to be technical in nature – not so.

A router is a product – it was produced in a competitive environment. Someone said “this is what we need”, then someone else said “do we really need all that?” and then a minimal specification was created which internal and external parties competed on “who can make it cheapest?” (How formal or organic the process is differs but it’s still the same.)

Low boot-time was not an important part of the specification, probably not even considered at all, and as such suffered because there was no need for it and it would’ve cost more to make it faster – maybe not a lot more, but more is still more.

The router is a small computer. It‘s task is to negotiate all the information that is sent through your network. That requires some specific tasks that are carried out by different modules. And those power up in a specific sequence. Between those steps, there are also set timers, to make sure one step is finished before the other starts.

The big ELI5 is that a router is designed to stay on for a long, long time so optimizing the time it takes to start up isn’t so important