bitmindframes

Planning & Cabling Networks

Media Required to Make a LAN Connection:

LANs use gateways to connect o other networks.
They use hubs or switches to connect end devices.
Each port on a router connects to a different network.
Routers break up broadcast domains and collision domains.
Routers can have both LAN and WAN interfaces.

Intranetwork Devices:

Hub

Receives signals, regenerates and sends them over all ports.
Creates a logical bus (i.e. multi-access media, everybody is on the same wire). [topologies].
Shared bandwidth approach – reduced performance (only one device can talk at a time).
A single collision domain.
Less expensive than switches.

Switch

Receives frames and regenerates them to a destination port.
Segments a network into multiple collision domains.
Reduces the collisions on a LAN (almost eliminate them).
Each port creates a separate collision domain.
A logical point-to-point topology to the device on each port.
Dedicated bandwidth per port increased performance.
Can be used to connect segments of different speeds (1Gb to switch and 100Mb to desktop, etc.,).
More expensive than hubs, but enhanced performance and reliability make them cost effective (more redundancy)
Cost
Determined by capacity and features.
# and types of ports (port density, 12/14/24 etc….).
Switching speed.
Network management capabilities, security, etc….
1 large central switch vs. smaller distributed switches.
A single central switch can be a single point of failure.
Redundancy: a secondary central switch and/or multiple connections between switches.
The goal of redundancy is to allow the network to continue even if one device fails.

Factors to Consider in choosing a Router:

Cost, interface types/speeds.
Additional factors.
Expandability (ie modularity).
Media.
OS Features.

Security.
QoS.
VoIP.
Additional Layer 3 protocols e.g. IPv6.
Special services: e.g. NAT, DHCP.

Types of Connections in a LAN:

When planning LAN cabling, there are 4 areas to consider:

1. Work area.
2. Telecom room (i.e. distribution facility).
3. Backbone cabling (i.e. vertical cabling).
4. Distribution cabling (i.e. horizontal cabling).

Total Cable Length.
EIA/TIA 568B – combined length in all areas limited to 100m including 5m patch cord at either end.

Work Areas:

Locations devoted to end devices used by users.
Have a minimum of two jacks.
Standards specifies UTP patch cords = max of 10 meters (in total, 5m at each end).
Straight-through cables most common.
Hubs/switches in this area typically use a crossover cable to the wall jack (like devices).

Telecommunications Room:

Contain hubs, switches, routers, and DSUs.
Provide transitions between backbone and horizontal cabling.
May also contain the servers used by the network.
Horizontal Cabling:

Connects telco rooms with work areas. Max 90m.

Backbone Cabling (AKA vertical cabling):
Connects teleco rooms to equipment rooms (servers).
Sometimes routed outside the building to WAN or ISP.
Used for aggregated traffic so typically require higher bandwidth (i.e. fiber), [different types of tfc frm different switches/users].

Types of Media:

UTP (Category 5, 5e, 6, and 7).
Fiber-optics.
Wireless.
Each has advantages and disadvantages.
Factors to consider:

Cable length.
Cost.
Bandwidth.
Ease of installation.
Susceptibility to EMI/RFI.

Cable Length:

Includes all cables from end devices to devices in telco room.
Attenuation = loss of signal strength as it travels along media.
Cabling distance is significant for data signal performance.

Cost:

Fiber material and installation costs are significantly higher.
Fiber performance is not required in most environments.
Maximize cost/performance ratio.
Servers generally need more bandwidth.
Fiber may be right for a server connection.
Fiber offers the greatest bandwidth and potential for future.
Wireless is also supporting huge increases in bandwidth, but it has limitations in distance and power consumption.

Cabling Factors:

Ease of installation.
Varies according to cable types and building architecture.
Floor/roof spaces, and the physical size/properties of cable influence how easily it is installed.
Cables are typically installed in raceways – enclosures that protect cables and keeps them neat and easy to thread.
UTP – lightweight, flexible, small diameter, RJ-45 plugs.
Relatively easy to install and standard for all Ethernet devices.
Fiber – issues with bend radius, crimps and variety of connectors (ST, SC, MT-RJ). More difficult to install.
Wireless networks require cabling to connect WAPs (wireless access point).
Wireless is easier, but many external factors can effect it.
EMI and RFI must be considered when choosing a media.
Can be produced by electrical equipment and lighting.
To connect buildings fiber is usually the best choice.
Wireless interference must be identified and minimized.

Making LAN connections:

RJ-45: pins 1 to 8.

Straight-through and Crossover UTP Cables.
Crossover Cable G/GW switched with O/OW
Types of interfaces:

In UTP Ethernet, devices use either MDI (Media Dependent Interface) or MDIX (Media Dependent Interface – Crossover).
MDI uses normal Ethernet pin-out: Tx: 1 & 2, Rx: 3 & 6
Computers, servers and routers use MDI.
Hubs/switches – MDIX, they swap Tx pairs (internally by default).
Connecting different devices Straight Through (ST).
Connecting similar devices crossover (XO). [like devices].
Router and a PC are really both computers therefore are like devices and must have a XO to connect them together.
ST has identical wiring on both ends that are terminated the same in accordance with either the T568A or T568B standards.
Use ST cables for the following connections:

Switch to router Ethernet port.
Computer to switch.
Computer to hub.

Crossovers:

Terminated so Tx from device A is wired to Rx on device B and vice versa. These “XO” connections give this type of cable its name, crossover.
One end – T568A and the other = T568b
o 1 to 3, 2 to 6, 3 to 1, 6 to 2.
Pins 1 and 2 crossover with pins 3 and 6.
Use XO cables for the following connections:

Switch to switch.
Switch to Hub.
Hub to Hub.
Router to router Ethernet port connection.
Computer to computer.
Computer to a router Ethernet port.

1. A physical switch or toggle that can be used to change between MDI and MDIX.
2. An OS configuration command can be issued to change that (Cisco devices).
3. MDIX auto-detection and configuration.
Identify the correct cable to use in connecting intermediate and end devices in a LAN (online material has a good diagram).

WAN connections include:

Telephone lines – RJ11 (e.g. DSL).
60 pin Serial connections – 2 forms (on the Cisco end).
1. DB-60 connectors (old green).
2. Smart Serial connector (new blue).
Both have a male Winchester connector (V.35) at other end which normally connects to a CSU/DSU (Channel Service Unit, Data Service Unit).

DCE & DTE:

DCE – supplies clocking services (CSU/DSU).

Typically at ISP end of the link.

DTE – receives clocking services (e.g. Router).
In our labs one router will have to be a DCE.

This router must have a DCE cable (female V.35).
Configure terminal emulator (Hyper Terminal).

Use a rollover cable to connect to router/switch.

Open hyper terminal and enter:

Bits per second: 9600bps.
Data bits: 8.
Parity: N = None.
Stop bits: 1.
Flow control: None.

Tags: switch, ip, 802.1q, vtp, vlan, study