CNNA3-Chapter 6 docx

• Traditional Inter-VLAN Routing:• One router interface per VLAN.. • Traditional Inter-VLAN Routing:• Traditional routing requires routers to have multiple physical interfaces to facili

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Chapter 6 Inter-VLAN Routing

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Inter-VLAN Routing Introducing Inter-VLAN Routing

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• What is Inter-VLAN Routing?

• Each VLAN is a unique broadcast domain.

• Computers on separate VLANs are, by default, not able to communicate

• Each VLAN is a unique IP subnetwork.

• To allow VLANs to communicate, we need a router to communicate among separate broadcast domains and unique IP subnetworks

• Inter-VLAN routing, then, is a process of forwarding traffic

Introducing Inter-VLAN Routing

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• Methods:

• Traditional Inter-VLAN Routing.

• Router-on-a-stick Inter-VLAN Routing.

• Switch Based Inter-VLAN Routing.

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• Traditional Inter-VLAN Routing:

• One router interface per VLAN.

VLAN Tagged

Internally Routed to the proper subnet

Tagremoved

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• Router-on-a-stick Inter-VLAN Routing:

• One router interface for all VLANs.

VLAN Tagged

Internally Routed to the proper subnet

Tagremoved

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• Layer 3 Switch Inter-VLAN Routing:

• Uses Switch Virtual Interfaces (SVI) to retag

the frame

VLAN Tagged(10)

Tagremoved

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• Traditional routing requires routers to have multiple

physical interfaces to facilitate inter-VLAN routing

• Each interface is also configured with an IP address for the subnet associated with the particular VLAN that it is connected to

• In this configuration, network devices can use the router

as a gateway to access the devices connected to the other VLANs

Interfaces and Subinterfaces

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Traditional Inter-VLAN Routing

Traditional Inter-VLAN RoutingInterfaces and Subinterfaces

TaggedVLAN 10

TaggedVLAN 10RemovedTag

TagRemoved

Router Responds

to Port F0/1

Router tagsthe framefor VLAN 30And switches it

to Port F0/1

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Traditional Inter-VLAN Routing

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• Traditional inter-VLAN

routing using physicalinterfaces does have alimitation

• As the number of VLANs

increases on a network, thephysical approach of having one router interface per VLAN quickly becomes hindered by the physical

hardware limitations of a router

• Routers have a limited number of physical interfaces that they can use to connect to different VLANs

• It is very expensive to add an Ethernet Interface

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• Subinterfaces:

• Overcomes the hardware limitation of a router

• Subinterfaces are software-based virtual interfaces

that are assigned to physical interfaces

• Each subinterface is configured with its own IP address, subnet mask, and unique VLAN assignment

• Connected to a switch trunk link

• Functionally the same as using the traditional routing model

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Router-on-a-stick Inter-VLAN Routing

TaggedVLAN 10

TaggedVLAN 10RemovedTag

TagRemoved

TaggedVLAN 30

TagRemoved

TagRemovedVLAN 30Tagged

TaggedVLAN 30RemovedTagTag

Removed

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• Configuring Subinterfaces:

• Similar to configuring physical interfaces.

• Create the subinterface.

• Assign it to a VLAN.

• Assign an IP Address.

• Enable the interface.

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• Create the subinterface:

• The syntax for the subinterface is always the physical interface, followed by a period and a subinterface

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• Assign it to a VLAN:

• Before assigning an IP Address, the interface must to

be configured to operate on a specific VLAN using the proper encapsulation

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• Assign an IP Address:

• The IP Address assigned here will become the default gateway for that VLAN

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• Enable the interface:

• Subinterfaces are not enabled individually.

• When the physical interface is enabled, all associated subinterfaces are enabled

R1(config-if)#no shutdown

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VLAN 10

VLAN 10VLAN 10VLAN 10

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Planning!

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• Router Interface and Subinterface Comparison:

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Inter-VLAN Routing Configuring Inter-VLAN Routing

(Putting It All Together)

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Configuring Inter-VLAN Routing

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Trunk in Native VLAN

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Enable All Subinterfaces

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Inter-VLAN Routing Troubleshooting Inter-VLAN Routing

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• Switch Configuration Issues:VLAN 30 is working but VLAN 10 cannot communicate with the

Interface F0/4 is still in the default VLAN

switchport access vlan 10

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• Switch Configuration Issues:

Each of the configured subinterfaces is unable to send or receive VLAN traffic

Interface F0/5 is still in the default VLAN

switchport mode trunk

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• Router Configuration Issues:

PC1 cannot communicate with the router interface and the router cannot route to VLAN 30

Switch port F0/4 is for VLAN 10

Move the cable from F0/9 to F0/4

One of the most common mistakes in Inter-VLAN routing

Move the cable from F0/9 to F0/4

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• Router Configuration Issues:

PC1 cannot communicate with the router interface and the router cannot route to VLAN 30

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• IP Addressing Issues:

Incorrect IP address for

subnet 172.16.10.0/24.Incorrect subnet mask for subnet 172.16.10.0/24.

Incorrect subnet mask for

subnet 172.16.10.0/24

PC1 cannot communicate

Tiêu đề	Inter-VLAN Routing
Trường học	Unknown University
Chuyên ngành	Computer Networking
Thể loại	lecture notes

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Số trang	33
Dung lượng	2,91 MB