Networking: Antennas and IPsIntroduction to networkingA network is a set of computers that are connected to the same interface so that they can share information over the network.

There is one device that manages the connections between the computers. This device is called the router. To recognize each computer in the network, it assigns one direction to each one. This direction is called IP. The IP is an ID of four blocks of numbers separated with a dot (i.e. 192.168.1.12). Each block goes between 0 and 255.

Apart from the directions that are associated to the devices, we have some extra IPs:

• The IP of the network is the ID that characterizes the network itself. We know when a IP is the networks' one because the last block of numbers is a 0 (i.e. 192.168.1.0).

• The IP of the router is the ID of the router. The last block of numbers is usually a 1 (i.e. 192.168.1.1).

• The IP which last block is the number 255 is reserved to broadcast. Broadcast is always necessary and it is used when one computer wants to communicate with all the others. So, when we type 192.168.1.255, we are referring to all the computers connected to the network.

How do we assign an IP to the network?

Actually, there are three different categories of networks. The distinction between them are the number of devices that can be connected to the same network.

An IP can be divided into to two big blocks. The first one is the network-part, and the second is the host-part. For example, in the IP 192.168.1.xxx, the network part is 192.168.1 and the host part is the number between 0 and 255 represented here by xxx. So, in this case, we will be able to connect 254 (254+broadcast) devices in the network. This IP is from class C, and this class is the one we used in the project. Following the example, the IP of the network will be 192.168.1.0, the IP of the router 192.168.1.1, and then the IP of the devices can vary from 192.168.1.2 to 192.168.1.254.

In the Sawla scheme, we used this three IPs: 192.168.0.0, 192.168.1.0, 192.168.2.0. The IP of the routers are 192.168.0.1, 192.168.1.1, 192.168.2.1.

Library. ICT center St Agustine'sAntennas' network

In Sawla, we created 3 networks. The first network is the library's one (192.168.2.0), the second network is used to interconnect both centers using antennas, and the last one is associated to St. Agustine's (192.168.1.0).

Not only does the router interconnect different devices in a single network, but also has the function of interconnecting different networks. As we will see, the router and the antenna are physically included in the same device: the Ubiquity Nanostation M5.

As just explained, the Ubiquity Nanostation M5 has two interfaces (two different networks): LAN and WAN. LAN means Local Area Network, it uses Ethernet cable and is associated with the schools. The St. Agustine's school is the LAN1, and the Library-ICT center is the LAN2. WAN means Wide area network, it uses Wireless and its function is to interconnect 2 LANs. Our WAN is the Antennas' network, so the antennas are connecting one to each other using wireless (WiFi).

In the interconnection, there are two antennas: the master and the slave. The master is the one who creates the wireless network, and the slave is the one who is connected to the network.

To sum up, the Nanostation has two IPs. The Nanostation 1 will have the LAN IP 192.168.2.1 (router) and the WAN IP 192.168.0.1 (antenna master). The Nanostation 2 will have the LAN IP 192.168.1.1 (router) and the WAN IP 192.168.0.2 (antenna slave).

Apart from the router, there is a device called Switch. The only function that the switch provides is to extend the number of computers that can be connected to a router. For instance, if we want to connect 16 computers in the same network, and our router just have 4 ethernet connections, we will need 3 switches of 4 ports so that the connection can be successfully done. Moreover, the switch does not have an IP.

How do we assign the IPs to the other devices?

There are two different ways to asign IPs to the computers and antennas.

• Static IP: We assign the IPs manually buy entering the set up of the device.

• DHCP: There is a program called DHCP which aim is to assign one IP to every device that is connected to the network. To do that, we provide a list of possible IPs, for example between the range 192.168.1.2-192.168.1.254; and the DHCP program assigns automatically the IPs.

The

antenna: Ubiquity Nanostation M5The antenna is a device that is connected to a LAN through Ethernet, and connected to the WAN through WiFi (Wireless).

DHCP mode ON DHCP mode ONStatic IPs