WANs are the method used to connect LANs together. Because of the long distances involved we will normally have to use a third party company known as a telecommunications company or ‘telco’ to provide us with this service.

SECURING THE ROUTER

Network security has never been so important than it is now. There are literally thousands of hackers operating all over the world constantly scanning IP addresses and ports trying to gain access to your PC or network equipment.

ADDRESS RESOLUTION PROTOCOL (ARP)

ARP resolves a known IP address to a MAC address. When a host needs to transfer data across the network it needs to know the other hosts MAC address. The host checks its ARP cache and if the MAC address is not there it sends out an ARP broadcast message to find the host.

STATIC ROUTING

Static routes are very common in modern networks. The administrator tells the router that to get to a particular network either leave a certain router interface or go to the next router (or the next ‘hop’). Configuring your routes in this way gives very precise control of what traffic goes where on your network.

IP ADDRESSING

An IP address is made up from binary numbers which are grouped into octets. The reason for this is that when IP addressing was first conceived it was determined that this amount would be more than enough for many years to come.

SPANNING TREE PROTOCOL (STP)

Layer 2 LAN protocols have no method to stop traffic endlessly travelling around possibly carrying inaccurate information. At layer 3 we can make packets die after a certain amount of time or after they have travelled a certain distance. It quickly became evident that a system to prevent loops was needed if LANs were to continue to function.

CONNECTING TO A ROUTER

When you buy a router it normally comes with no configuration on it whatsoever. The administrator must configure the router from scratch according to the particular requirements of his or her network.

NETWORKING EQUIPMENT

A computer network can be as small as two computers joined together by a single cable to the largest network in the world – the internet.

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Primary TCP/IP Port Assignments and Descriptions

TCP/IP provides a total of 65,535 ports of which 1023 are considered to be well known ports. In reality the number of ports that are used by popular network clients and services comprises an even smaller subset of the well known group of ports. The following table lists the functions of this subset.