Tài liệu giảng dạy CCNA - module 04 chapter 13-Cisco LAN Switching Basics

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Module 04 LAN Switching
Chapter 13
Cisco LAN Switching Basics
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Table of Content
1
The Case for Bridging and Switching
2
LAN Switching
3
LAN Segmentation
4
The Need for Spanning Tree
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1. The Case for Bridging and
Switching
4
Collisions domain: Share access

Limits the number of computers
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Collisions domain: Repeater

Propagate collisions
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Collisions domain: HUB

Propagate collisions
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Collisions domain


Collision Domains are the area where collisions occur.

All of layer 1 interconnections are part of the collision domain.

Extending a network with a repeater or a hub, results in a
larger collision domain.
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Segmenting Collision Domain
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LAN Segmentation With Bridges
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0
Layer 2 bridging
00000CAAAAAA
A
B
C D
00000CBBBBBB
00000CCCCCCC
00000CDDDDDD
00000CAAAAAA 00000CDDDDD
1
2
MAC Address Port
00000CAAAAAA 1
00000CBBBBBB 1
00000CCCCCCC 2
00000CDDDDDD 2
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How Switches And Bridges Learn
Addresses

Reading the source MAC address of each received frame

Recording the port on which the MAC address was received

If the address is not found, the bridge forwards the frame out all
ports except the port on which it was received.

If the address is found in an address table and the address is
associated with the port on which it was received, the frame is
discarded.

If the address is found in an address table and the address is
not associated with the port on which it was received, the bridge
forwards the frame to the port associated with the address.
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2
How Switches And Bridges Filter
Frames

Bridges are capable of filtering frames based on any Layer
2 fields

Most Ethernet bridges can filter broadcast and multicast
frames

Today, bridges are also able to filter according to the

network-layer protocol
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Transparent Bridging

Transparent bridging is called “transparent” because the
endpoint devices do not need to know that the bridge(s)
exist(s).

In other words, the computers attached to the LAN do not
behave any differently in the presence or absence of
transparent bridges.
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4
2. LAN Switching
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5
Switch operation

A multi port bridge.

Micro-segment

Support full duplex.

Hardware switching.

Dynamically builds and maintains a Content-Addressable
Memory (CAM) table.
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Half-duplex Networks
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Full-duplex Transmitting

Full-duplex Ethernet allows the transmission of a packet
and the reception of a different packet at the same time.

This connection is considered point-to-point and is collision
free

Full-duplex Ethernet offers 100% of the bandwidth in both
directions
Full-Duplex
10 or 100 Mbps
10 or 100 Mbps
10 or 100 Mbps 10 or 100 Mbps
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Microsegmentation Implementation
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Switch modes
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0
Switch modes

Store-and-forward:


The entire frame is received before forward.

The latency is greater with larger frames.

Error detection is high.

Must be used for asynchronous switching.

Cut-through:

The switch reads the destination address before
receiving the entire frame.

The frame is then forwarded before the entire frame
arrives.

Fast-forward and Fragment-free switching.
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3. LAN Segmentation
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2
LAN Segmentation
Isolate traffic between segment achieve more bandwidth
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3
LAN Segmentation With Bridges
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LAN Segmentation With Routers

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5
LAN Segmentation With Switches
•
Switches eliminate the impacts of collisions
through the micro-segmentation
•
Work with existing 802.3(CSMA/CD)