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New Member

VLANs necessary?

Hi,

An easy one for you gurus; I have a router which will have a /21 range on its Ethernet interface. I want to split this into a number of variable length subnets. Am I obliged to split this interface into a number of subinterfaces? e.g. if a packet for a /26 address belonging to my /21 will it get routed to the eth interface if I just set up a static route for this address range to that interface?

(sorry if I'm being unclear)

Thanks

1 ACCEPTED SOLUTION

Accepted Solutions

Re: VLANs necessary?

Hi Eav,

Create subinterfaces on router and give a command encapsulation dot1q under that subinterface.

Each subinteraface will have different subnet ip address as you want. Now the cable coming from that port on router will connect to the switchport and you have to configure that switchport as trunk port.

You also have to configure number of vlan on your switch for which you want subinterfaces on router and can assign ports on switch to those vlans and connect the workstation.

Once you are done you can assign the workstation respective subnet ip range as you have defined on subinterfaces and gateway address remain the samne which is your respective subinterface ip address.

No static routes are needed to route between the subnets as all the subinterfaces are directly connetec interfaces so routing will happen automatically.

This configuration is known as intervlan routing or we can router on stick.

Check this link for example topology and sample configuration

http://www.cisco.com/en/US/tech/tk389/tk390/technologies_configuration_example09186a00800949fd.shtml#output

HTH

Ankur

2 REPLIES

Re: VLANs necessary?

Hi Eav,

Create subinterfaces on router and give a command encapsulation dot1q under that subinterface.

Each subinteraface will have different subnet ip address as you want. Now the cable coming from that port on router will connect to the switchport and you have to configure that switchport as trunk port.

You also have to configure number of vlan on your switch for which you want subinterfaces on router and can assign ports on switch to those vlans and connect the workstation.

Once you are done you can assign the workstation respective subnet ip range as you have defined on subinterfaces and gateway address remain the samne which is your respective subinterface ip address.

No static routes are needed to route between the subnets as all the subinterfaces are directly connetec interfaces so routing will happen automatically.

This configuration is known as intervlan routing or we can router on stick.

Check this link for example topology and sample configuration

http://www.cisco.com/en/US/tech/tk389/tk390/technologies_configuration_example09186a00800949fd.shtml#output

HTH

Ankur

New Member

Re: VLANs necessary?

That's great ANkur, thanks for your help!

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