Wireless networking has evolved rapidly over the past few years, when it first came out hardware was very expensive and for the most part unreliable, speeds were poor and security was a big issue, this has all changed now of course and wireless networks are expanding and playing a bigger part in home and corporate networks around the world.

For those who are considering implementing a wireless network it is important for you to realise the differences between them (apart from the obvious of course!) so let’s take a look:

Convenience – Wireless networks offer huge convenience benefits over standard wired networks. With a wirelessly connected device you can move around and still stay connected providing you are in range. This is great for office users who are frequently moving from office to office and for just about any scenario when you want to be outside or are not sat close to the nearest switch. Wireless connectivity offers a huge freedom that a wired network will never be able to do.

Performance and speed – Whilst wireless technology has had some huge advancements with the latest wireless N suite it is still nowhere near capable of gigabit speeds that can be found in wired networks. The biggest issue with wireless speed is fluctuation and the fact that the speed you get will depend a lot on your distance between the nearest access point and whatever happens to be in between the wireless device and the access point itself. This is a factor that will always be present with wireless networking. With a wired network you will always get the speed that the wire is capable of (providing there is no flaw in the cable) and the speed you get today will be the speed you get tomorrow and the day after and so on.

Whilst wireless N is theoretically capable of 300mbps it is unlikely we will see these kinds of speeds for a long time! In fact it is safe to assume that 100mbps is the maximum throughput you are likely to see, and this is under perfect working conditions (i.e. perfect line of sight and very good range to the access point). The other problem is that an upgrade from wireless G to wireless N can be expensive, especially in a large distributed wireless network.

Security – Probably the biggest issue with wireless networking is the security aspect. By default if no encryption is used your wireless network would be exposed to absolutely anybody who is in range. These means that a hacker could intercept all the traffic travelling between you and the wireless router or access point. Stepping up from this you have WEP encryption which is extremely unsecure and can be comprised with relative ease and freely available software. Luckily WPA and WPA/2 address these issues an offer a more robust security algorithm. With a strong pass phrase you can ensure that hackers are going to have a very tough time breaking into your network.

With wired networks this kind of concern isn’t applicable and security issues will stem from how well your network equipment is physically secured and from the kind of protection you are using that will stop external intruders (firewall, access-lists etc)

Reliability – If setup correctly a wireless network can be very reliable, however for a large one there are many factors to consider and the whole process can get very expensive. Without proper consideration for the environment that it will operate it and the conditions, wireless networks can be very unreliable. Signals can fluctuate and speeds can drop, in worst case scenarios you can experience frequent disconnections that can be very annoying. Wired networks on the other hand will very rarely give you any problems, under normal conditions the cables will last a very long time and the switches (if from a reputable manufacture) will last many many years.

The Cisco CCNA certification is a great way of starting a career path in networking. With the CCNA under your belt you will have some great practical knowledge of how networks operate and the different types of hardware and technologies that drive them.

If you are studying for the CCNA you want to ideally be able to practice configurations that you come across in your course material, to do this you have one of two options. You can either buy some old Cisco routers and switches from eBay and setup your own home lab environment or you can use some virtual lab software like the network visualizer 6.0. The first option can get expensive, especially if you want to practice some of the more advanced configurations where you need to multiple routers and switches. The second option on the other hand is a lot cheaper, a lot easier and takes up a lot less room!

With the CCNA Network Visualiser you can put a complex network together in a matter of minutes; it uses a simple drag interface with single buttons to add each device. The list of devices you can add are:

• Host PC
• 2621 Router
• 2811 Router
• 1900 Switch
• 2950 Switch
• 2960 Switch
• 3550 Switch
• 3560 Switch

The interfaces on the devices vary but generally you will be using the Fast Ethernet and Serial interfaces to link your network together.

There is no real limit to how many devices you can add so you can technically create some very large networks! When you click on a device you will presented with a larger view of the device and you can then click an interface to connect it up to another device. The level of detail is more than sufficient for the CCNA objectives. For example clicking a serial device will prompt you for whether you want to have it as a DTE or DCE device, depending which you choose you might have to provide clocking in your configuration.

If you are adding hosts you can assign them a static ip address and bring up a command prompt to test connectivity between hosts. The only working commands for the command prompt that I could find to use were ping and telnet. In all fairness these are the only two that you will really to test connectivity in your network.

Configuring the devices is a simple as double clicking them to bring up the console window. The console window will look and act just like a real Cisco router. You are able to use the function shortcuts (like CTRL+A to go to the start of the line) and typing a ? will bring up a list of available commands.

Like I said, configuring the devices is exactly the same as it would be with a real Cisco device. You can setup telnet access and configure it from another router or from a device; you can change hostnames and perform basic router changes.

But the stuff you’re really going to want to do is configuring routing protocols like RIP, OSPF and EIGRP. Providing you configure all your devices correctly these routing protocols will work and propagate routing tables throughout the network. The same thing goes for setting up vlans and vlan routing between devices, if they are configured properly they will operate just as they would in a normal network.

Sadly there are a few commands that you might come across that you want to try out but can’t even though they are covered in the CCNA objectives. The ones I found were changing the encapsulation type on a VLAN trunk link, it will not allow you and will come up with ‘Unknown Command’ (Even though if you use the ? it will show you the command is there!). You will also not be able to use the crypto command to setup SSH access. For the most part though you should be able to complete all the test labs you need for the CCNA exam – basic router commands, routing protocols, vlans, spanning-tree, access-lists, nat, WAN (Frame relay) and ipv6. Even though every single command is listed using the ?, you will not be able to use a lot of them; only the ones covered in the ccna objectives.

Summary – Overall this is a great little piece of software, it allows you to quickly design and configure networks of all sizes, you can add some pretty scalable configurations in here with as many devices as you want. 95% of what you need for the CCNA objectives are covered with the commands you can use here. However if wanted to play around with other commands or for those that are covered in the CCNP you will struggle with this. But for the CCNA this is perfect and could save you a lot of time, space and money.

Check out the CCNA Network Visualizer 6.0 at the official routersim homepage.

The subnet mask is an intricate part of your network connection configuration. If you’ve ever needed to set a static IP address for any reason you’ve probably wondered what to put in the subnet mask field. The subnet mask is what tells your machine which part of your IP address is the network portion and which part is the host portion. To explain this best let me quickly go through what an IP address is made up of.

The IP address – An IP version 4 address is 32bits long and split into 4 octets (four 8 bit sections), for example: 22.56.90.189.  Imagine that each bit of the address can either be a 1 or a 0 and then at each octet can be from 0 (all off) to 255 (all on). Check out the below for a visualisation.

This particular block would be a 0 because all the bits are turned off. If we turned the first bit on (to a 1) then this block would be 128. This is the binary mathematics behind an IP address and the same principle applies to the subnet mask. Remember I said about network and host portions? This is basically to identify what network you belong to. Consider the following IP address and subnet mask:

IP Address – 192.168.1.55
Subnet Mask – 255.255.255.0

The way that the subnet mask works is that all bits that are turned on are the network bits, and all bits turned off are the host bits. In this example we had to turn all bits on in the first 3 octets to give us 255.255.255. The 0 block obviously has no bits turned on and this is the host block. So this would mean that our network is 192.168.168.x or 192.168.168.0. This means that anything in the fourth octet is a host, apart from 2 exceptions which I’m going to talk about!

The network address: The network is used to represent all hosts in a network; it is used by routing tables to make decisions based on individual networks as opposed to individual hosts. In a standard subnet mask like 255.255.255.0 the network id would be 0 because it is the first number within the network (remember we go from 0 to 255). So in this example our network address is 192.168.1.0

The broadcast address: This is the address that is reserved to send a ‘broadcast’ to all hosts within a network. It is a special address and is the last usable address in a network, so in this example the broadcast address would be 192.168.1.255.

Unless you are subnetting for any reason then your subnet mask is going to be standard, and if you are using a private IP address of 192.168.something.something then your mask should be 255.255.255.0. If you were using a class b private address (172.16.something.something – 172.31.something.something) then your mask should be 255.255.0.0. Finally if you were using a class A address (10.something.something.something) then your mask should be 255.0.0.0.

Subnetting – I could devote several pages to subnetting as it is indeed a tricky thing to get to grips with. What subnetting does is split a network into two or more smaller networks. When you do this your subnet mask will no longer be standard. Unless you have any special requirements in your home network you shouldn’t really need to subnet.

If you want to view your subnet mask then click start and run (or just type in the search box) cmd and click ok. In the command prompt type ipconfig and press enter. You will be shown your ip address, subnet mask and default gateway.