What is the difference between a router and a modem?

(By Modem, we’re assuming you mean a cable (DOCSIS) modem or a DSL modem)

To the user, the difference is that a modem provides a single ethernet port that will provide a single IP address and connection for a single device. So, you could pug a laptop or a desktop into it, and that would be it. It doesn’t provide a DHCP server or a firewall or NAT (that you need to connected multiple devices at a time) or any kind of wireless, and you shouldn’t really do this.

The modem does a lot of other things to connect to the ISP’s network, converting the cable system or DSL signals to an understandable ethernet connection. Fun fact: The name modem is actually a contraction of the two words MOdulator DEModulator

Now the router: There are many types and sizes of router, but sticking with the domestic kind, a router allows you connect an Internet connection (the WAN or Wide Area Network) to multiple devices on a LAN (Local Area Network). In most consumer devices, it includes a 4 port switch, a wireless access point, and software that is a firewall, a DHCP server, and a NAT translator. It also routes packets from the WAN to the LAN and vice versa.

Some ISP’s such as Comcast or Verizon FiOS will provide a combined modem and router in a single device, so it can be a single unit between the coax or fiber from the ISP and all your wired and wireless devices. While this is neater, it does somewhat limit your functionality and control. Most people call this a ‘router’ but it is in fact a modem/router.

I always recommend having a separate modem and your own router. That way you’re not tied to your ISP when you want to upgrade your wireless or change your firewall settings.


What's the difference between WiFi and Ethernet?

A few stipulations:

  1. Bandwidth isn’t speed. Bandwidth is capacity. Speed is latency aka delay. Increases in latency visibly impact your user experience more than decreases in bandwidth in most cases.

  2. Wired Ethernet is always lower latency and higher bandwidth than WiFi, i.e. always better.


The amount of latency increase and bandwidth reduction you will experience by using WiFi vs wired Ethernet depends on many factors.

  1. What bands and protocols your router or access point supports

  2. What bands and protocols your client supports

  3. How far the router is from the client

  4. How much material (walls etc) is between the router and the client

  5. How much interference is in the air (from both WiFi and non-WiFi sources)

  6. How many other devices are connected to the same radio

If you have a router and a client that support 802.11ac with wide channels, and you stand next to the router, your bandwidth may reduce somewhat (probably it will still be more than your ISP connection for most domestic users) and your latency will probably be close to double that of wired.

As you move further away, the router will reduce the channel width and step down the data rate to maintain the connection, until it hits the minimum. If it’s set up that way, your device may swap to a lower level protocol and reduce data rate further.

As you get further away or get behind more obstacles, the signal will eventually become unusable.

The range of expected behavior would be that your bandwidth would reduce by anywhere from 80–90% of wired all the way down to 5 or 10% depending on conditions, and your latency will go from double to 10x and beyond.

It all depends on your application. If you’re streaming or gaming, any increase in latency is mostly unacceptable. If you’re checking Instagram, in many cases you won’t even notice.


Why is a wired connection better than a wireless connection?

[Assume you are asking about a wired Ethernet connection vs a WiFi connection, with all other factors being equal]

A wired connection is better than a wireless connection because:

  1. It has a lower latency (i.e. improved response/speed)

  2. It has more consistent throughput (bandwidth)

  3. It is much less prone to interference

  4. It is more secure

  5. It is less expensive (although these days it’s not usually a factor)

  6. It is the same throughput, capacity and speed (latency) at 50 or 100 meters as it is at 5 meters distance.

WiFi is OK in a single family home with minimal interference for devices such as tablets and phones that have no other option. However, you will always receive better overall performance from a wired connection; the best rule is that if you have to plug it in for AC power, plug it into an Ethernet jack. Smart TV’s, media streamers, gaming consoles, NAS devices etc will always work better wired than wireless.


How many connections can be established with a 100 mbs internet connection?

The answer to this, strictly speaking, depends on the device that’s between you and the Internet connection. Assuming it’s a NAT gateway of some sort, and you have private IP space on your side, and a single publicly routed IP on the connection side, then there will be connection limits baked into your NAT gateway. They are normally much higher than you will normally run into.

If your NAT gateway runs some form of Linux (most appliances do) this limit will be what is known as the Conntrack limit in proc/sys/net/ipv4/ip_conntrack_max (This link tells you more than you probably want to know Connection tracking ) It’s probably 64K connections on most larger devices. it can be increased, but that has a RAM penalty of about 1 Gigabyte per 64K connections.

If you run into the limit, there are also aging and timeout values that can be adjusted.

We manage one network that has exceeded 64K connections, but that’s a very busy one. Remember that one device or host can have dozens or even hundreds of connections, so this isn’t one connection per device.

We can’t think of any other connection limits that would limit the number of connections other than MAC address table limits. If you have a particular use/case I could maybe give a more appropriate answer.


​How long can a Cat7e Ethernet cable be before it starts to lose connection speeds?

​100 meters is a spec limitation. However, worth pointing out that Cat7e and Cat 6 will perform much the same at 100 m at 1 Gigabit per second. There’s no performance benefit to be gained from Cat7e.

​If you want to go further than 100m, use single mode fiber. You can buy it in pre-terminated lengths if you’re not inclined to splicing it yourself, and SFP and SFP+ optics have got much, much cheaper in the last few years.


How can you tell if an Internet Service provider (ISP) is throttling your internet speed?

​Firstly, except for being limited to your maximum subscribed bandwidth, most (we would say all) fixed Internet connections are not throttled by the ISP.

​All situations we have seen where people though the ISP was throttling them have turned out to be something else, usually

a) It’s a cable modem, and it slows down at peak times just through workload rather than throttling or

b) WiFi is involved somehow.

​There’s no reason an ISP would throttle your bandwidth unless you had a data cap and that’s not common on a fixed connection.


I believe all devices connected the router in my home will have the same public address. Does it mean that I cannot host a website on same port on 2 computers in my home which are connected to the same router?

​The answer is yes and no. First of all you need to have a static public IP address from your ISP, not one allocated by DHCP as that will change. That static address needs to be pointed to by the DNS name that you are going to use, say www.foo.com.

Once you have that, you need to forward port 80 (HTTP) and 443 (HTTPS) and any other ports you might need to the internal non-routable address that your server has (which also needs to either be non-DHCP allocated, i.e. static or to have a DHCP reservation for it’s MAC address in your router).

​So now you have one website.

​If your web server supports host headers, you can set up multiple websites on the same server (Microsoft’s IIS will do this), and their DNS entries can point to the same (single) public IP. The important distinction is that you have multiple websites, but they’re on the same web server, i.e. have the same IP address. It works fine.

​If you need to use multiple physical servers, then the only way you can do it is to use different port numbers - say 8000 for http - which means you’d need to access it via www.foo.com:8000 which isn’t very helpful.

​Better to use a larger computer, a single web server, and host multiple sites.

​What are the advantages and disadvantages of fiber vs Ethernet cable when connecting two switches together?

​Fiber advantages:

  • Can operate at much higher data rates and carry multiple signals

  • Virtually Immune to electro-magnetic interference

  • Can cover much greater distances point to point with a single run

Fiber disadvantages:

  • Cost - wire is more than copper, terminations are significantly more

  • Has a limited bend radius (i.e. you have to curve it gently)

  • To attain it’s potential greater data rates, both switches must support higher rate transceivers (10 GbE, 40 GbE optics etc), and then you have to purchase the transceivers.

​Essentially, 1 Gigabit on copper and 1 Gigabit on fiber over a couple of hundred feet in a normal environment will perform almost exactly the same, but the fiber will cost more.

​If you need to go more than 300 feet, or need more than 1 Gigabit, or have a lot of electromagnetic interference, fiber is the way to go.

​In a home network, is it beneficial to use Ethernet with Powerline adapters for certain devices, and leave Wi-Fi for streaming HD video?

For anything like streaming or gaming, use ethernet (Cat6 cable). Yes, it’s a hassle to run wires, but it will work better than anything else, period. There’s a simple rule, if you plug it in for power, plug it in for Ethernet.

​WiFi is fine for trivial applications, or if you have no other choice. It’s not the best technical solution for anything - it trades performance for convenience and it’s subject to interference.

​Powerline is not a bad middle route if you absolutely can’t run Cat6.


What is the best way to set up Verizon fios with your own equipment?

[Assume you mean without using the Verizon supplied router]

FiOS doesn’t use a free-standing modem in the way that cable systems do, it uses a fixed device called an ONT (Optical Network Terminal). This is a powered device that converts the signal from the fiber that leads up to your house or apartments int a signal that you can use.

The normal way that FiOS is set up is with a coaxial cable from the ONT to a Verizon supplied router (You might be paying for this, you don’t need to). If you want to use your own equipment, you don’t want that to happen. The ONT has an RJ45 handoff (i.e. normal wired ethernet). If you request it, Verizon will provide the ‘hand-off’ on the RJ45 rather than the coax, and you can just connect a Cat6 Ethernet cable between the RJ45 on the ONT and the WAN port on your router (or whatever equipment you are connecting).

Note that you have to specifically request this, Verizon will always use the coax by default.


How good are fiber optic internet cable connections?

​Let’s first define how we understand you question: we think you’re asking how good Internet is when delivered on a fiber optic service, not how good are the various ways of connecting an FO cable (e.g APC, UPC etc).

​In the US context (and probably most other countries) a cable company - that in the industry we call MSO’s (think Comcast, Spectrum, Cox etc) - doesn’t deliver direct to consumer on fiber optics. They use what’s called HFC networks (Hybrid Fiber Coax) that use fiber to get to the neighborhood and then coax to get to each consumer. That isn’t a fiber connection, that’s just the same old cable that slows down when everyone gets home in the evening.

​Fiber to the home delivers a fiber right up to your house. The best known FTTH service in the US is probably Verizon FiOS. In common with other regional fiber providers, this uses a single fiber strand per subscriber and a technology called GPON.

​If that’s what you have, you have one of the best consumer connections available. GPON delivered over fiber is stable, reliable, and delivers it’s capacity promises in terms of bandwidth. It just works, every time you need it to.

​So, hoping we’ve answered the correct question - the answer is excellent...probably.


How can I troubleshoot and get in-wall Ethernet ports working?

​Here’s the troubleshooting:

(we're assuming that one end is connected to a switch, and on the other end you have a device, and it isn’t working)

  1. Take a look inside the in-wall jack. Does it have paint in it? One of the most common reasons for wall jack fails is being painted, and paint getting on the conductors. This can be temporarily fixed with some careful scraping and a Q-tip, but the jack should probably be replaced.

  2. Undo the plate from the wall. Visually inspect the wires. Anything loose or astray? Visually inspect the wire at the patch panel end. Anything loose or astray? Most fails happen at one end or the other.

  3. Next, replace the jack. Physical mechanical fails happen because of repeated connects & disconnects. *Always* re-terminate both ends of a drop at the same time - when you replace the jack, make sure you re-terminate both ends, and that you use the same color code standard. You’ll need a 110 punch down tool for termination in most cases.

  4. If that doesn’t fix things, you probably have a break in the wall. To identify that you’ll need a Time Domain Reflectometer or TDR that will tell you where the break is, and on what pair. Some higher end switches have this function built in. If you don’t have access to a TDR, you’ll need to re-pull the wire, and that’s a whole different story.


Can a wireless modem, after being dropped, result in one's personal computer being slower?

​Potentially yes, if the connected computer is connected using wireless, and the drop resulted in the modem/router’s antennae (either internal or external) becoming damaged or misaligned. Compare performance with a wired connection using the same computer and modem/router. Check both latency and throughput (bandwidth). You should expect wireless throughput to be half or less than the wired throughput, and the latency to be higher.

​If you’ve suddenly had a wireless performance loss, the most common reason would be the introduction of some strong interference affecting the signal.


How is bandwidth distributed among connected devices in a single WiFi network?

​Effectively, first come first served, unless specific rate limits are assigned by the wireless AP, Switches, or gateway device.


Can you get a high speed internet in the middle of nowhere, like a mountain cottage?

​It really depends on your definition of High speed. You can get satellite Internet almost anywhere in the continental USA with Hughes. (HughesNet® Internet |1-855-386-1643 | Satellite Internet) They advertise up to 25 Mb/sec *but* be aware that physics dictates that the latency will be high. You won’t be doing video conferencing with one of these.

​If you have the money you can rent your own space segment and use commercial VSAT but that would be ridiculously expensive.


What is the difference between connecting to Wi-Fi and to the switch?

Essentially, the difference is that the connection will be faster, higher capacity, and more stable, secure and reliable.

All good reasons for doing this.

Of course you have to be within 100m/300ft of the switch, and you’re tethered with a cable.

It’s *always* recommended to connect with an ethernet cable wired rather than wireless where that option is available.


Someone threatened to "fry" my router. Can they actually do that and what can I do to prevent it?

This is probably bluster, but there are ways of ‘frying’, ‘toasting’ or just plain ol’ killing a router.

  • Applying excess voltage to an Ethernet connection to the router;

  • Using a HERF (High Energy Radio Frequency) device to destroy it from a distance.

    NOTE: Doing either of these things is extremely dangerous and potentially illegal depending on where you live. DO NOT under any circumstances attempt to apply incorrect voltages to any equipment or use a HERF device. This answer is provided solely to answer an academic question.


So - make sure this person can’t physically access or get near your router.


What is meant by bidirectional optical fiber?

In most business networks where you see fiber, you’ll see a plug in transceiver at each end of a connection, and two strands of fiber connected to each. The patch cords that connect them look something like this:


One strand is TX (Transmit) and the other is RX (Receive) to achieve duplex communication using the same wavelength.

What I believe you are referring to is transceivers that use a single, rather than two strands to achieve a duplex connection by running RX and TX at different wavelengths. This is a function of the transceiver rather than the fiber itself though.

Most fiber to the home deployments also use a single strand (and so are bidirectional).