Building HotSpot

Ever wonder how to build your very own wifi hotspot? If you followed my previous posts, I hope you manage to build your own home network and that is suffice for the first step in building wifi hotspot.

Next things to consider are how to manage your network, you certainly don't want anyone just joining your wireless network right? that is if you don't want to build free for all hotspot.

You also don't want people eating all your bandwidth, somehow you need to limit the hotspot users, and limit their access so they won't be able to join your internal LAN.

If you want these features in your hotspot, you probably going to need something that is called captive portal.

What captive portal does is like this, if someone join your wireless network, he or she then open a web browser, the captive portal would then redirect the browser to your html page, no matter what url requested.
That html page of yours is typically a welcome page or a login page so only certain people can make use of your wireless network.
This is great for public wifi hotspots.

There are many captive portals that you can find, free or commercial ones, the one that I'm familiar with is from publicIP, it's called ZoneCD.

Most of the captive portals that you can find might work the same way, they need you to put a PC between your wireless device and your internal network or internet router.
This is the image I got from the publicIP ZoneCD:


The PC should have 2 NIC (Network Interface Card), one goes to your internal LAN, the other goes to wireless LAN.
That PC would do all the authentication of the wireless users, the bandwidth limitation, etc.

What I like most about ZoneCD is that it's a Live CD, you just need a working PC, put in the CD and then the PC boots from the CD, nothing needs to be installed.
Sure it's based on Linux/UNIX, but you don't need to know anything about Linux, you only need to know how to operate a PC, so they say.

You can do homepage redirection, content filtering for porn sites or downloads, the ZoneCD has built in firewall, you can also modify the login page to conform your own taste or give it a logo of your company.

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Subnet Calculator

One of the biggest challenges to design your local area network and for taking the CCNA exam is calculating subnets.
Actually to calculate subnets is quite easy but it can be confusing for networking newbies. And luckily there are many tools out there that can help us in this problem.

One of the tools is Boson Subnet Calculator, you can download this tool for free from Boson. This thing is very handy, it can calculate subnets, find out which subnet an address belongs to, do a wildcard checking, and have a Decimal IP Calculator.

 

 The only thing you need to do to find what addresses belong to a subnet is just insert the IP address of a computer to the Host IP and slide the Mask bit to match your subnet mask.

As the above picture, I typed in 172.16.10.5 and subnet mask of 255.255.248.0. Immediately I know what addresses for that subnet, you can see them at the Current Host Range.

This tool also valuable to learn subnetting since it shows how it calculates the subnet, recommended for companion to pass CCNA exam.

Too bad you can't use this at the CCNA exam.

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Network Segmentation

You started your network with small amount of computers and networking devices, sooner or later you want to add this and that, next thing you know your network got slower.

If you have this condition in your network, you might want to consider reviewing back you what devices you have in your network. You might need to segment your network.

You can use switches and bridges to segment your network, if you use them you separate your network collision domain. Remember what collision domain is when I posted about switches.

Like the above picture, if you use switch to connect 4 computers, then you'd have 4 collision domains. On the other hand, if you use hub, then you'd have 1 big collision domain, this will not only slow your network but also pose security problems.

The above picture looks good, but they're still count as one broadcast domain. To break up broadcast domain you can use routers.


What broadcast means is that computers need to send packet all over the network. One example is when you use DHCP to give IP address to all computers, first the computers will send out DHCP Discover message everywhere saying, help I don't know my IP, can anyone give me one?
The fact that computers send a lot of broadcast when connected to a network, the more computers/broadcasts you have, the slower your network will be.

 

When using router to break broadcast domain like this, this means you'd have 2 broadcast domains, in other words, you have 2 network segments within your network.

In CCNA exam, they usually give questions like this, if you have a network with the diagram like the above picture, how many broadcast domains and collision domains exist?

You know you have 2 broadcast domains, but how many collision domains? 

Remember each port in a switch forms one collision domain and routers also the same.

From the above we can tell that the diagram has 6 collision domains.

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Managing Cables in Racks

You typically find bulks of cables like the left picture shows in a project. It's not strange to have a project with 2000 clients to be connected in a network.

To arrange cables like these is a nightmare for network installers if you don't provide yourselves with cable managers.

Usually the cable managers also provided by the racks vendors. You can ask them if they have it, or use cable managers from other vendors if you don't like the way it looks.

Different cable managers have different ways to manage cables, so it's better to consult the vendors on how to install the cables according their products.

I need to remind you that some cable managers make the look of your racks neater but if you don't install them accordingly, they will make your future improvement harder. What I mean is that you have to design also how the cables run inside your rack should be. You don't want the outer look of your rack looks neat while you have spaghetti cables inside.

This is how one of the cable manager from ADC Krone looks like

And me and my team manage to make the upper picture look like this

Well it looks better then the last picture at least.
Like I said vendors develop their own cable managers, another example is from Systimax down here

The vendors  even develop many cable managers for desktop computers/end users. You can find many of them out there, so, start browse for cable managers to manage your cabling, don't let the cables to be an eyesore.

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Common Home Networking Topology

The following picture shows the common network topology of home networking:

There you can see some of the devices that I talked about. If you use cable internet then you need a cable modem which mostly be provided by the ISP.

You don't actually need a router if you just one to use 1 computer for internet. But if you want to share the internet connection, you'll need additional router for connecting the computers.

But if you use ADSL, you can use ADSL router, there are plenty cheap ADSL router out there. You don't need the modem.

After modem and router, you'll need switch which provide a lot of ports that you can use to connect your computers. The good news is that routers these days come with built-in switch ports, so you don't need to buy additional switch. Mostly the routers have 4 built-in switch ports.

If you want to connect using wireless, you'll need Access Points. Here you can connect your laptops, hand held devices that support wireless connection, and even your gaming console like PSP or XBOX360.

Another good news is that there are routers that also have a built-in Access Point and built-in switch ports - hah - you only need 1 device for your network.

To set the devices are easy work, some vendors also provide installation cd so you can follow all the instruction in the cd. But I promise you it is very easy to make your network up and running.

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Cable Trays for Enterprise Networking

In an enterprise environment there should be thousands if not millions of cables running around for data connectivity. Managing all those cables can be very frustrating if you don't carefully design the cable placement and everything else.
That's why most modern buildings nowadays have cable trays in place just on top of the ceilings. The reasons to use cable trays are obvious, to keep the cables from tangling and to keep cables used for different purposes away from other cables, e.g. networking cables away from electrical cables to prevent interference.

 

The pictures above show how the cables are arranged at cable trays, you can see that the cables - gray cables for UTP cables, blue cables for fiber optic cables, and black cables for electric cables - are separated and arranged.
In reality, sometimes you can't easily arrange them like that, because the cable installers/contractors are commonly different for networking cables, electrical cables, and even for the cable trays installation. As network installers, we surely want to keep our cables away from the electric cables, while other not-so-professional installers or contractors won't even care of it. The point is to always keep smooth communication with other contractors within a project.

The cable trays carry the cables from the telecommunication rooms to the end users, you can see the exposed trays like at the pictures above typically located at the telecommunication rooms. While the trays to the end users are covered on top of the ceiling.
Below you can see the trays heading to the racks, just imagine to arrange all those cables.

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