Switching Lecture 01

8/6/2019 Switching Lecture 01

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2002, Cisco Systems, Inc. All rights reserved.


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2002, Cisco Systems, Inc. All rights reserved. 2

Configuring Catalyst Switch

OperationsModule 3


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2002, Cisco Systems, Inc. All rights reserved. ICND v2.03-3

Objectives

Upon completing this module, you will be able to:

Explain how bridging and switching operates

Explain the purpose and operations of the Spanning-

Tree Protocol

Verify the default configuration of the device, given afunctioning access layer switch

Build a functional access switch configuration to

support the specified network operational parameters,given a network design

Execute an add, move, or change on an access layerswitch, given a new network requirement


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2002, Cisco Systems, Inc. All rights reserved. 4

Basic Layer 2 Switching and

Bridging Functions


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Objectives

Upon completing this lesson, you will beable to:

Describe Layer 2 switching and bridgingoperations and modes

Describe how LAN switches use and populatethe MAC address table


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Address learning

Forward/filter decision

Loop avoidance

Ethernet Switches and Bridges


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Cut-Through

Switch checks destination

address and immediately

begins forwarding frame.

Fragment-Free

Switch checks the first 64 bytes,

then immediatelybegins forwarding frame.

Store and Forward

Complete frame is received

and checked before

forwarding.

Transmitting Frames


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A default switching method for Distribution Layer Switches

Latency: High

Error checking: Yes

Store and Forward


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It is also referred as modified cut-through

A default switching method for Access Layer Switches

Latency: Medium

Error Checking: On 64 bytes of Frame

Fragment Free


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A default switching method for the Core Layer Switches

Latency: Low

Error Checking: No

Latency: It is the total time taken for a frame to pass through the switch.

Latency depends on the switching mode and the hardware capabilities of the

switch.

Cut-Through


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MAC Address Table

Initial MAC address table is empty.


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Learning Addresses

Station A sends a frame to station C.

Switch caches the MAC address of station A to port E0 bylearning the source address of data frames.

The frame from station A to station C is flooded out to all

ports except port E0 (unknown unicasts are flooded).


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Learning Addresses (Cont.)

Station D sends a frame to station C.

Switch caches the MAC address of station D to port E3 bylearning the source address of data frames.

The frame from station D to station C is flooded out to all ports

except port E3 (unknown unicasts are flooded).


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Filtering Frames

Station A sends a frame to station C.

Destination is known; frame is not flooded.


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Filtering Frames (Cont.)

Station A sends a frame to station B.

The switch has the address for station B in the MACaddress table.


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Station D sends a broadcast or multicast frame.

Broadcast and multicast frames are flooded to all portsother than the originating port.

Broadcast and Multicast Frames


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Summary

Ethernet switches and bridges increase the availablebandwidth of a network by creating dedicated networksegments and interconnecting the segments.

Switches and bridges use one of three operating modesto transmit frames: store and forward, cut-through, andfragment-free.

Switches and bridges maintain a MAC address table tostore address-to-port mappings so it can determine thelocations of connected devices.

When a frame arrives with a known destination address,it is forwarded only on the specific port connected tothe destination station.


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Switching Lecture 01

Documents

Transcript of Switching Lecture 01