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

6.7 Review

In this part you will briefly review the different roles the home gateway plays in a home network.

Now watch the video below, which is about 2 minutes long.


Download this video clip.Video player: 40_review.mp4
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We’ve seen that a home gateway carries out a number of different roles.

The crucial role – the reason we call it a gateway – is that it is the gateway from the LAN to the rest of the internet. This is because it is a router, able to pass packets from its inside interface to the outside interface, from the LAN to the internet.

In fact, the same box is also acting as a switch, dealing with local traffic on the LAN, for example computer to printer, computer to tablet, and so on. It does this both for wired and wireless traffic.

It’s also a wireless access point, so that devices can connect to the LAN using Wi-Fi as well as wired Ethernet.

To connect to the internet, it may include a modem able to convert from Ethernet to broadband phone line for example.

It will also be working as a DHCP server, responsible for configuring devices that connect to the LAN.

The local configuration is very likely to use private addresses, so the gateway will have to carry out network address translation, NAT, so that devices can communicate with the internet.

The gateway may also act as a firewall, protecting the network against malicious attack. We haven’t discussed the details of firewalls, but techniques include inspecting IP packets, which the gateway is doing for NAT in any case.

Besides being set up as a DHCP server, some gateways will be set up as DNS servers.

And they also include a web server, because that is needed to display the configuration pages so you can manage the gateway from another device on the LAN.

And for some purposes, the gateway will act as a client – it may get its own configuration by connecting to an ISP’s central DHCP server, for example.

So taken as a whole, overall the typical home gateway is really quite a capable device.

End transcript
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Activity 6 Think about

10 minutes

Your ISP has given you a new, updated gateway. Could you use your old gateway device as a second wireless access point? What would you need to consider?


Yes, it should be possible to use your old gateway device as an additional wireless access point. Once set up, the old box will no longer be a ‘gateway’ but it will use the Wi-Fi and switching functions. Routing, NAT, DHCP and DNS will all be carried out by the new gateway.

Some gateways have a configuration option to set this up automatically; otherwise, you can do it manually. This is easier if you plan to connect the old box to the new gateway with an Ethernet cable connection; trying to connect between old and new boxes by Wi-Fi is challenging or impossible.

Since both old and new gateways may by default have the same IP address, do the initial setup of the old box using a cable connection from a laptop. Change the inside IP address of the old box to be a static address on the same network as the new gateway but which doesn’t clash. Disable DHCP on the old box.

Connect the old box (use a LAN port, not the port labelled ‘internet’ or ‘WAN’ since you are not using the routing functions) by cable to the new gateway. You should now be able to connect to your home network and the internet through either Wi-Fi point; your mobile device should pick the better connection, or you can pick manually if you have kept different SSIDs.


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