Planning And Cabling To The Network
There are many considerations to make when planning the network. In this section we will consider the LAN connections and the WAN. The choice of which router to deploy is determined by the Ethernet interfaces that match the technology of the switches at the center of the LAN. The internetwork devices that we will be using in this course will be primarily routers and switches.
The routers in our networks are used to interconnect the various LAN networks. Each LAN is usually connected to others using an interface on the router. The router has various LAN interfaces that it connects to these segments. Therefore, when choosing a router, you should consider the number of LANs in your global network. The router should also have interfaces that connect to outside interfaces such as to an ISP.
The figure shown below shows the various ports that can be found on a router as well as explanations on their use.
- The fast Ethernet interface will be used to connect to our LAN networks while the serial interface will be used to connect to the WAN.
- The console port is the main configuration port on a router, and it is where we will connect to the router and issue configuration commands through. The auxiliary port shown as aux port is used as an alternative to the console port.
- The power button on a router is used to turn on and off the router.
The switch will be used to connect to the various end user devices in our network. These may be PCs, notebooks, IP phones among others. The switch is connected to the router using one of its interfaces so that other networks can be reached through the router.
The image shown below shows a 48 port CISCO switch.
Device selection factors
In our networks, there are several factors that will affect which devices we will install. These factors may affect network performance and may be influenced by the factors shown below.
Cost – the various models of CISCO routers and switches, the choice of router or switch may be influenced by the budget that the organization may have.
The speed of the ports on a device may influence the decision to install a particular device. We will learn about the various speeds and how they influence the network performance in upcoming chapters.
Other factors that may influence our choice of device are the manageability of a device, support, durability, whether it has expansion bays, among others.
Whatever device is chosen for your network, however, the successful implementation of the network will depend on the configuration and careful planning that has been done.
Cabling The Network
When cabling the network there are several factors to consider.
- The length of the cable
- Telecoms room
- Backbone and distribution cabling
- Environmental factors
The length of the cable is one of the most important factors to consider. In most networks we will use the UTP (Unshielded Twisted Pair) cable. This cable is made of copper the range should be limited to 100 meters.
Telecommunications room – in many organizations, this is the central area where intermediary devices such as routers, backbone switches, among others are located. The cabling in this room should be correctly labeled so as to avoid misconfiguration and other problems.
Backbone cables are the cables used to connect to devices such as servers, distribution cables connect to end user devices and are mainly straight through UTP cables.
When cabling the network, there are several types of cables that may be used. We will discuss the use of the UTP cable and the serial cables.
The UTP cable will be used to connect the following devices
- Router to router – depending on scenario
- Router to switch
- Router to PC – or other hosts end devices
- Switch to switch
- Switch to hosts.
These configurations use three main types of UTP cable configurations which are.
- Straight through
- Cross over
- Rollover cable
TIA/EIA governs the UTP cabling standards, the figure below shows an example of the UTP cable. It has four pairs of cables with different color codes.
There are 8 wires in pairs. These are
The two T568 standards i.e T568A and T568B, determine the arrangement of these wires so as to suit the various configuration needs.
T568A and T568B arrangements are shown in the image below.
These configurations are constant and cannot change.
- Straight through configuration – both sides of the UTP cable have the same standard i.e both are either T568A or T568B.
- Crossover cable configuration – one end is T568A the other end T568B.
Where to use these cables
The straight through cable is used to connect devices that work on different layers of the OSI models. i.e
- Routers and hosts such as PCs work on layer 3 – logical addressing
- Switches work on layer 2 – physical or MAC addressing
Therefore, to interconnect a router to a switch or a switch to a PC, we use a straight through cable.
To interconnect devices working on the same layer in the OSI model, we use crossover cables. Ie – switch to switch, router to router and router to PC.
The table below shows the various connections used in the LAN using these standards.
|Device 1||Device 2||Cable type|
|Router||Switch||Straight through cable|
|Switch||Router||Straight through cable|
|Switch||PC||Straight through cable|