cisco

Chapter 1
LAN Design

Switched LAN Architecture
When building a LAN that satisfies the needs of a s mall or medium-sized business, your plan is more li kely to be
successful if a hierarchical design model is used.
Divided into discrete layers.
Each layer has a specific purpose.
Becomes modular – maintenance, performance.

Switched LAN Architecture
Access Layer
Interfaces with end devices.
Routers, switches, bridges, wireless access points.
Provides a means of connecting and controlling whic h devices are allowed to communicate on the network .
Distribution Layer
Aggregates (funnels) Access Layer traffic.
Controls traffic flow with security or routing poli cies.
Defines broadcast domains.
Routing of VLANs (Virtual LANs).
Core Layer
High speed backbone of the network.
Must be highly available and redundant.
Must be capable of quickly forwarding large amounts of data.
Smaller networks – collapsed model (Core and Distri bution).

Medium Sized Business
Benefits of a Hierarchical Network
Scalability (can be expanded easily)
Redundancy (at the core & distribution layers ensur e availability)
Performance (link aggregation & high performance di strib. & core layer switches provide near-wire speed at all
layers.)
Security (port security at the access layer & polic ies at the distrib. Layer make the network more sec ure.)
Manageability (consistency among switches at each l ayer makes management more simple.)
Maintainability (modular design allows a network to scale easily w/o becoming over-complicated/burdens ome.)

Principles of Hierarchical Network Design

- Just because a network is hierarchical, it doesn’t mean it’s well designed.
Network Diameter:
The number of devices that a packet has to cross be fore it reaches its destination.
For PC1 to communicate with PC3, the data must trav erse 6 intermediate switches.
In this case, the network diameter is 6.
Each switch introduces some latency.
In a hierarchical network, network diameter is alwa ys going to be a predictable number of hops between the source
and destination devices.
Bandwidth Aggregation:
After the bandwidth requirements of the network are known, links between specific switches can be aggregated or
combined to provide higher bandwidth.
Link aggregation allows multiple switch port links to be combined so as to achieve higher throughput b etween
switches.
The determining factor is using link aggregation is the requirements of the user applications.
Redundancy:
The practice of providing multiple paths to a desti nation or multiple instances of a device.
Redundancy is one part of creating a highly availab le network.
Multiple links between switches or multiple devices .
It can get expensive and most likely will not be do ne on the access layer because of the cost and vari ety of devices.
It is feasible at the distribution and core layers.
What is a Converged Network?
A Converged Network is one where voice and video communications have be en combined on a single data network.
Legacy Equipment:
Until now, mainly feasible on large enterprise netw orks.
Advanced Technology:
More popular to medium and small sized businesses.
Can be a difficult decision considering current inv estments in technology.
Benefit:
Only one network to manage.
New Options:
You can now tie voice and video communications dire ctly into an employee's personal computer system.
Software integrated on a PC eliminates an expensive handset.
Add a webcam and video conference.

LAN Design (Matching Switches to specific LAN funct ions)
Considerations for Network Switches
Traffic Flow Analysis:
The process of measuring the bandwidth usage on a n etwork and analyzing the data.

Performance tuning.
Capacity planning.
Hardware improvement decisions.
User Community Analysis:
The process of identifying various groupings of use rs and their impact on network performance.
Data Stores and Data Servers Analysis:
When analyzing traffic on a network, consider the l ocation of the data stores and data servers.
Consider both client-server and server-server traffic.
Topology Diagram:
A graphical representation of a network infrastruct ure.
Switch connections with port numbers.
Aggregated ports and redundant paths.
Identify configuration by switch name.
Could contain user information.


Switch Features
Switch Form Factors:
When selecting a switch, you need to decide between
Fixed configuration or modular configuration.
Stackable or non-stackable.
The