When we talk router we tend to think of a single device, but that device is really made up of several key components so before we get to bridge mode we need to understand a little bit about what makes devices tick.
The internet uses IP Addresses to identify everything on the internet, they are like phone numbers - when you want to send information you need to know the phone number..
There are also two types - Public and Private, for this the important thing to know is that you are given a public IP address by your ISP, and it's managed by your router. When you browse to a website or play a movie; that address is how all that data finds its way back to you.
Making a router
If you wanted to make a router you would need four key components…
|A Modem||A modem is a bit like a translator on one side it talks DSL and on the other data that we can use. This is the bit that deals with the wire that comes from the wall.|
A router decides where the packets that arrive should go, it basically decides if something is destined for the internet or for another device on your network.
The device is actually named after this component as it's so important and manages everything such as firewalls and NAT.
|A Switch||The switch is a distribution engine, it connects the ports on the back.|
|A Wi-Fi Access Point||We have to have Wi-Fi right? The access point allows it to talk over Wi-FI|
Manufacturers though have noticed that there are different types of modem, there is DSL, Cable, Fibre which presented them with a choice.
Create different products for each possible option.
This adds cost both to the manufacturer and us, and isn't ideal people will buy the wrong one, but where it's common enough like VDSL it's worth it.
Don't have a modem.
In the professional space all these boxes are separate, that means you can get the right devices for your need, manufacturers can offer the products for less, and have less versions reducing costs even further.
For a consumer it also means that if you move from VDSL to Fibre your awesome router is still awesome and works fine.
You still need a modem, that box that translates from the wall to your router, one way to do this is to keep your old router, and connect the two…
But this has a problem known as Double NAT…
What is NAT and Double NAT
NAT stands for Network Address Translation, That's a bit in depth to talk about now but It's how your router allows all your devices to use your internet, It's like the dealer at a blackjack table, making sure that all the bits of data go to where they should.
It's super important….
Double NAT is when you do it twice, so you multiple devices doing that Network Translation between your device and the internet.. most of the time this is fine, but confusion can be caused when one is expecting data to arrive in a particular way but doesn't tell the other, causing the dealer to drop cards because he just doesn't know where to send them.
When you use bridge mode you are telling your router, to go dumb, it's trying to be clever and doing work with things like NAT that we actually don't want. So were specifically telling it to do it's modem thing but just pass the data back.
So your old router just acts as a middle man, that's why it's called a bridge.
It achieves this by Letting your new router handle your Public IP, and making itself invisible. It relies completely on your new router to deal with all the details about connecting to your ISP, Public IP's, Firewalls, dealing with NAT and everything else you want a router to do.
If your router supports bridge mode, you don't need one but not all routers do or they were never designed to support it correctly and at times like this it's better to buy a dedicated device.
You can also find that with a dedicated modem you actually get a better internet connection simply due to higher quality components and a device being designed to do one thing really well.
The thing to remember though - that dedicated modem It's still working in Bridge Mode.