Discovering computer networks: hands on in the Open Networking Lab
Discovering computer networks: hands on in the Open Networking Lab

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Discovering computer networks: hands on in the Open Networking Lab

1.2 The home gateway and network settings

In this part you will take a closer look at the home gateway and in particular ways of finding more information about home network settings. This will help you to:

  • investigate your own home gateway and network settings
  • understand the significance of some of the information you find.

There are three short videos to watch and several activities. When you have completed this part, you should be able to find information on your own home gateway. You should know the role of IPv4 and MAC addresses and recognise their format.

Watch the video below, which is about 6 minutes long. This shows you how to find information about your network using the Microsoft Windows settings page.

Using the Windows settings page

Download this video clip.Video player: 04_using_the_windows_setting_page.mp4
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Transcript

As you can imagine, your home gateway is a complex piece of equipment. Just think of all the tasks it has to do. Via the internet, it receives data from outside the LAN and directs it to a destination within the LAN, and it receives data from within the LAN and sends it out onto the internet.

In this and the next two videos I’m going to introduce you to three different ways of finding information about your home gateway and network settings. I’ll do this by investigating my own network. However, I’ll only be discussing some and not all of the information we’ll see there. Because I’m currently working on my laptop which is connected to my home network via Wi-Fi, much of the information will relate to my wireless network. If my laptop was connected to my home gateway by cable instead we’d be seeing something slightly different.

OK. In this video I’ll look at finding information through the Windows Settings menu. You can reach the Settings page from the Windows Start menu. Click on the settings icon to take you to Windows Settings. From here, click on the Network and Internet icon … then Wi-Fi followed by Hardware properties.

This is the Wi-Fi settings page. I’ll just run through some of the information you’ll find here.

SSID stands for service set identifier. It’s the name associated with a wireless LAN (abbreviated as WLAN) and is used for identification by devices wanting to connect to it.

The next four items give more information about my wireless network.

This one here – ‘Protocol’ – identifies the wireless protocol operating on the wireless LAN. A protocol is a just a set of rules for doing something. Wi-Fi is governed by a set of international standards so that it’s the same everywhere (more or less). These standards are administered by the Institute of Electrical and Electronics Engineers (abbreviated as IEEE) but known as I triple E and they all have the number 802.11. These standards get updated from time to time so a letter, or letters, are added to indicate the version of the standard. Here you can see that the one used on my wireless network is 802.11n.

Moving down to the next item: the security used on my wireless network is shown as ‘WPA2-Personal’. WPA stands for Wi-Fi Protected Access. It’s a protocol that’s been used since 2004 for the protection of wireless networks. WPA2-Personal is a version designed for home users and small businesses.

The next item – ‘Network band’ – gives information on the frequency band my network is using. It’s the 2.4 GHz band.

Moving down, the next item shows the channel used on the frequency band. This is something that’s automatically selected by the home gateway and it’s likely to change next time I connect. At the moment channel 1 is being used. Having a choice of transmission channels makes it possible to avoid contention with other nearby devices.

Two IPv4 addresses follow this so I’ll start by briefly explaining what an IPv4 address is, though you will be meeting IPv4 addresses again later in the course.

Every device participating in a computer network has an IP address assigned to it, and each IP address on a local network must be unique.

An IPv4 address is just a numeric identifier chosen from a pool of almost four thousand three hundred million possible addresses. By the way, IP stands for Internet Protocol which is the protocol used for sending data from one computer to another on the internet. For convenience, IPv4 addresses are written as four groups of decimal numbers from 0 to 255 separated by dots. You’ll often hear this referred to as ‘dotted decimal’ or ‘dotted denary’. In order to receive internet traffic, every device needs to have an IP address. Here you can see that the IPv4 address given for the wireless network adapter on my laptop is 192.168.2.5.

The second address shown here is labelled as ‘IPv4 DNS servers’ but in other contexts you might see this address labelled as ‘default gateway’. This is, in fact, the address of my home gateway and when my laptop wants to send data to my home gateway, this is the address it needs to use. It’s 192.168.2.1. I’ve already mentioned that a home gateway has multiple functions – one of which is to act as a DNS server to locate websites when you’re browsing the internet. DNS stands for Domain Name System. You’ll be learning more about DNS servers later, so I won’t say more about them here.

There’s also another address shown: the ‘Physical address (MAC)’. MAC stands for media access control. Like the IPv4 address, a MAC address (sometimes called the physical address or hardware address) is an identifier. Every computer network adaptor has one and each is unique. You can see that the MAC address is in a different format to the IPv4 address. This isn’t in dotted decimal and it includes letters as well as numbers, using a numbering system called hexadecimal. You’ll be learning about MAC addresses later in the course.

You may be wondering why my home gateway has both an IPv4 and a MAC address. Briefly, this is because these addresses are used in different ways at different times, and this is all you need to know for now.

So we’ve looked at the first method of finding information about your home gateway and network settings.

End transcript
 
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Activity 4 Try it out

5 minutes

Using the Windows settings page, find out and note the following:

  • the IP address of your home gateway

  • the IP address of your computer’s network card

  • the MAC address of your computer’s network card.

Discussion

Have you spotted that the first three parts of the IP address of your home gateway and the computer’s network card are identical? Further on in the course you’ll be finding out why.

Watch the video below, which is about 4 minutes long. It shows you how to find similar network information using the command prompt.

Using the command prompt

Download this video clip.Video player: 05_using_the_command_prompt.mp4
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Transcript

In this video I’m going to show you a second method for getting information about a network. This method uses the command prompt. (The command prompt just provides another way for you to interact with your operating system.) The quickest way to open the command prompt is to enter cmd into the Windows search bar and then click on the ‘Command Prompt desktop app’ option.

This opens the command-line interface which enables the user to interact with the computer by typing in commands. The ipconfig command will display all current network configuration values. So I’ll type in ipconfig followed by the Enter key.

You’ll see some information you should recognise from the previous video: the addresses 192.168.2.5 and 192.168.2.1 (here the address labelled ‘Default Gateway’ was called ‘IPv4 DNS servers’ in the previous video). But there’s something new: the ‘Subnet Mask’. Briefly, this stipulates that all allowed IP addresses on this network must have the form 192.168.2.X, where X is a number between 0 and 255.

Notice that the subnet mask consists of four dotted decimal numbers, just like the IP address. Where there’s a 255 in the mask, it means that the corresponding dotted decimal number in the IP address cannot be varied on this network. Doing so would produce a disallowed IP address for this network (though it may be OK on another one). So this subnet mask, 255.255.255.0, says that the viable addresses have three fixed numbers followed by a variable number.

Don’t worry if you feel a bit baffled by the idea of a subnet mask. You’ll be meeting it again later in the course where you should find this early but brief introduction was helpful.

Earlier on I said that when my laptop wants to send data to my home gateway, it needs to use the gateway’s IP address. Through the command-line interface there’s a very useful command that allows us to check whether the communication link between the two end points is working properly. The command is ping followed by the IP address at the end of the link we want to check. I’ll demonstrate this now to check the link between my laptop and my home gateway.

So I type in pingfollowed by my home gateway’s IP address 192.168.2.1.

You can see here that the ping command sends four packets of data to the IP address. In this context a packet is a data unit, though you will see it referred to by a different name in other contexts. When each packet is received a reply is sent back and at the end of the exchange some statistics are given. There is confirmation that four packets were sent, four received and none lost, and there’s a round-trip time given. The round trip is the time taken for the packet to be sent and the reply received. So in this example the ‘there and back’ journey between my laptop and my home gateway takes an average of one millisecond. One milliseconds is one thousandth of a second, so that’s pretty quick.

Next I’ll try pinging my tablet, which I know currently has an IP address of 192.168.2.3.

It’s no surprise that the round trip ping for this address took longer: 120 milliseconds on average. This is a more complex journey as the packet has to go through my home gateway to reach my tablet.

So now we’ve looked at the second method of finding information about your home gateway and network settings.

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Activity 5 Try it out

5 minutes

  • If you have more than one networked device (for example, a smartphone, a tablet, a second PC or laptop), check the allocated IP address of each device. (For smartphones and tablets you should find this in the settings pages.)

  • Using the command-line prompt, ping another device on your home network (for example, your home gateway, smartphone or tablet) from your home computer. Make a note of the average round-trip time.

Discussion

If your ping was unsuccessful, check that you haven’t made a mistake when entering the IP address.

Watch the video below, which is about 5 minutes long. It shows you a third method for finding network information – using a browser.

Using the web resource

Download this video clip.Video player: 06_using_the_web_resource.mp4
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Transcript

Now I’m going to show you the third method of finding information about your network. This method uses a web page. Do you remember that default gateway address we identified in the previous two activities? It was 192.168.2.1. Well, I’m going to enter it into my browser’s address bar. It may come as a surprise to you that you can enter an IP address into the address bar to access a web page instead of entering a URL. But a URL is just another form of IP address. So I press Enter and this takes me to a page for my modem-router setup.

If I wanted to alter any of the modem-router settings, I’d need to log in. However, I’m just checking information here. There’s a lot of information on this page and I don’t intend to discuss all of it, but just to focus in on some. Look in the LAN and WLAN settings sections. Do you recognise any of the information shown there?

You should recognise my wireless LAN SSID: Belkin_N+_D60294. Remember you saw that in the information revealed through the Wi-Fi settings page on my laptop. You should be able to recognise the address of my home gateway (here labelled as ‘IP Address’): 192.168.2.1 and also the subnet mask beneath it: 255.255.255.0. Both of these were revealed in earlier activities. In fact, my home gateway has two IP addresses: one (known as the private address) faces towards my local area network and one (known as the public address) faces towards the internet. The IP address 192.168.2.1 that was revealed in earlier activities is the private address.

To identify the public address of my home gateway, we need to look in the ‘Internet Settings’ section. Its labelled ‘WAN IP’ (remember that WAN stands for wide area network), and here it’s shown as 2.25.177.217. The ‘Default Gateway’ address, here shown as 213.1.113.60, is the address for my internet service provider (ISP).

Just for interest, I’ll try to ping both of these addresses. So I’ll go back to the command prompt that I left open from the last session and I’ll type in ping 2.25.177.217. Remember this is the public address of my home gateway. Again you’ll see that four packets of data were sent and the statistics given are: four sent, four received, none lost. Approximate round trip time in milliseconds this time: average 1 millisecond. So it’s the same. It’s the same time it took to ping the internal address – my private address. Not surprising really since they’re both in the same location. You’d expect them to take about the same time. So now I’ll ping my ISP’s gateway: ping 213.1.113.60 and Enter. So there’s another successful ping here. Four packets sent, four received, none lost. But this time the round trip in milliseconds is 13 milliseconds. So it’s taken a little bit longer for this packet to reach my ISP’s gateway and for a reply to be sent back. Not surprising: it has further to travel.

Public IP addresses can change frequently, so the next time I log on to my network I’m likely to see a different address. IP addresses that can change are known as dynamic addresses. You’ll learn more about these in later sessions.

So now you’ve seen the third way to find out more information about your home gateway and network settings.

End transcript
 
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Activity 6 Try it out

5 minutes

  • Use your home gateway’s web interface (as demonstrated in the video) to find and note down the following:
    • the external IP address of your home gateway
    • the IP address of your ISP.
  • Using the command-line prompt, ping a device outside your home network (for example, the public address of your home gateway or your ISP’s gateway) from your home computer. Make a note of the average round-trip time.
  • Compare the round-trip time when pinging a device in your home network (as previously noted) with the round-trip time when pinging a device outside your home network. What do they tell you about the connections between the two devices?

Answer

It takes longer for data to make the round-trip journey to a device outside your own home network than it does to make the journey to a device inside your own home network.

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