LAN Switching and Wireless Basic Switch Concepts and Configuration

LAN Switching and Wireless Basic Switch Concepts and Configuration

Objectives Summarize the operation of Ethernet as defined for

100/1000 Mbps LANs in the IEEE 802.3 standard.

Explain the functions that enable a switch to forward Ethernet frames in a LAN.

Configure a switch for operation in a network designed to support voice, video, and data transmissions.

Configure basic security on a switch that will operate in a network designed to support voice, video, and data transmissions.

Summarize the operation of Ethernet as defined for 100/1000 Mbps LANs in the IEEE 802.3 standard

Key elements of Ethernet/802.3 networks

Communication types reminder

Unicast – to a single host address e.g. most user traffic: http, ftp, smtp etc.

Broadcast – addressed to all hosts on the network e.g. ARP requests.

Multicast – to a group of devices e.g. routers running EIGRP, group of hosts using videoconferencing. IP addresses have first octet in range 224 – 239.

Summarize the operation of Ethernet as defined for 100/1000 Mbps LANs in the IEEE 802.3 standard

Design considerations for Ethernet/802.3 networks

Network Latency

NIC delay – time taken to put signals on medium from one end and to translate it on the other end.

Propagation delay – time spent travelling on medium

Latency from intermediate devices e.g. switch or router. Depends on number and type of devices. Routers add more latency than switches.

key elements of Ethernet 802.3 networks CSMA/CD (Carrier sense multi access /

Collision detection): it is the IEEE 802.3 standard.

• Carrier Sense

In CSMA/CD, all devices that have messages to send must listen before transmitting.

If a device detects a signal from another device, it waits before attempting to transmit.

When there is no traffic detected the device starts transmitting its message.

While this transmission is occurring, the device continues to listen for traffic on the LAN.

After the message is sent, the device returns to its default listening mode.

• Multi-access

If the signals of one device are not detected by a second device, the second device may also starts to transmit.

The media now has two devices transmitting messages at the same time.

The messages travel across the media and once they meet each other then a collision happens and the messages are destroyed.

Note: CSMA/CD is only used with half-duplex communication typically found in hubs. In full-duplex mode the collision detect circuit is disabled.

key elements of Ethernet 802.3 networks

Collision Detection

When a device is in listening mode, it can detects a collision that might happens in the media.

Jam Signal and Random Back off

When collision is detected, the transmitting devices send out a jamming signal.

The jamming signal notifies other devices of a collision and that they need to back off and stop transmitting for a random amount of time.

Explain the Functions that Enable a Switch to Forward Ethernet Frames in a LAN




Configure a Switch for Operation in a Network

Configure a Switch for Operation in a NetworkCisco IOS help facilities


Cisco IOS commands to access the command history



Prepare the switch to be configured


The basic switch configuration

console

Ethernet



Configure Basic Security on a Switch



Cisco IOS commands used to disable unused ports


Questions

Describe the operation of Ethernet as defined for 100/1000 Mbps LANs in the IEEE 802.3 standard.

What functions enable a switch to forward Ethernet frames in a LAN?

How do you configure a switch for operation in a network designed to support voice, video, and data transmissions?

Summary LAN Design

Process that explains how a LAN is to be implemented

Factors to consider in LAN design include

Collision domains

Broadcast domains

Network latency

LAN segmentation

Summary

Switch forwarding methods

Store & forward – used by Cisco Catalyst switches

Cut through – 2 types

Fast forwarding

Cut through

Summary

Symmetric switching

Switching is conducted between ports that have the same bandwidth

Asymmetric switching

Switching is conducted between ports that have unlike bandwidth

Summary

CISCO IOS CLI includes the following features

Built in help

Command history/options

Switch security

Password protection

Use of SSH for remote access

Port security

Documents

LAN Switching and Wireless Basic Switch Concepts and Configuration