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Internal

ODA040003 Inter-VLAN

Routing principle

ISSUE 1.3

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This course introduces the principle of

inter-vlan routing and layer 3 switch

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Upon completion of this course, you will

be able to:

Know the principle of Inter-vlan

routing

Understand the principle of layer 3

forwarding.

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Layer 2 switching network-broadcast

In traditional layer 2 switching networks, the whole network is abroadcast domain, so when the network increases in scale, networkbroadcasting severely increases, causing a drop in efficiency, whichis disadvantageous for management

Broadcast domain

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Insulating layer 2 broadcast domain

VLAN has insulated the layer 2 broadcast domain, thus strictly

insulate any flow between any two VLANs

VLAN 100 VLAN 200

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Inter-VLAN communication

Flows between different VLANs cannot directly cross VLAN

boundaries, we can use routers so that messages can be

transferred from one VLAN to another VLAN

VLAN 100 VLAN 200

VLAN 300

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Route selection in inter-VLAN communication

A default gateway is configured at the host; for non-local communication, the

host will automatically search for the default gateway, and send the

messages to the default gateway for transferring instead of directly sending

to the destination host

VLAN 100

1.1.1.10/24

VLAN 200

2.2.2.20/24

Ping 2.2.2.20Non-local communication

Using default gateway

network1.1.1.0/24 at interface 1

network2.2.2.0/24 at interface 2

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One physical connection for every VLAN

VLAN is configured on layer 2 switches, and every VLAN uses a

unique physical connection to one interface of the router.

VLAN 100 VLAN 200VLAN 300

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Use VLAN Trunking

multiple VLANs in the network can share only one physical link.

On the switch, configure that ports connecting to routers use the VLAN Trunking.

And make the same configuration in the router

VLAN 100 VLAN 200

VLAN 300

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Integration of switching and routing

Functional integration of layer 2 switches and routers forms the layer 3

switch; the layer 3 switch functionally realizes VLAN classification,

VLAN internal layer 2 switching and inter-VLAN route functions.

VLAN 100 VLAN 200

VLAN 300

VLAN 100 VLAN 200

VLAN 300

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Message to message Layer 3 switching technology

1

2

3

1

2

3

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2

3

1

2

3

Traditional layer 3 technology processes each message, and transfers

messages based on the destination IP addresses. This method iscalled from message to message

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Layer 3 switching technology based on flow switching

The first message

Subsequent messages

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2

3

1

2

3

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2

3

1

2

3

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Questions

How can the devices in different VLANs communicate with

each other?

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Inter-vlan routing principle

Summary

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