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New Member

Trunking on router interface

Hi,

Suppose i have a L2 switch and got VLAN100 and VLAN200 configured on it... The switch has got 1 link to the router and the router to internet...

I do not want VLAN100 and VLAN200 to communicate. Thus the switchport link i configure as trunk...

How abt the router interface? Can i set trunking but do not set the VLAN logical interface? Otherwise if i set the VLAN logical interface, inter-vlan routing will be enable rite?

Thanks

4 REPLIES
Gold

Re: Trunking on router interface

On the router, I assume you have a "Plus" version of the IOS so that you can do LAN subinterfaces for the VLAN trunking.

If you do not create one of the logical VLAN interfaces, and that is the only router, then traffic on that VLAN will be completely isolated. If that is what you want, then this is the easy way to do it.

If you create both VLAN interfaces, with routing enabled, then you will need access control lists applied to the interfaces in order to keep the VLANs from talking to each other.

Extended IP access lists can be configured to let you block VLAN 100 from talking to VLAN 200 (or VLAN 200 from talking to VLAN 100), and permit each VLAN to communicate with the Internet. If that is what you want. They can pretty much control the flow of traffic however you want it to be.

Hope this helps.

New Member

Re: Trunking on router interface

pls advise how shd i configure the LAN subinterfaces...

New Member

Re: Trunking on router interface

assume that you are using ether4/2, do not configure any ip address on ether4/2, then do the following:

conf t

ether4/2.1

encapsulation dot1q 100 (100 is the vlan id)

ip address x.x.x.x subnet mask

no shutdown

conf t

ether4/2.2

encapsulation dot1q 200 (200 is the vlan id)

ip address x.x.x.x subnet mask

no shutdown

I hope this will help you.

New Member

Re: Trunking on router interface

Try this link below. You will beed access-lists to block the vlans from talking.

http://www.cisco.com/warp/public/473/50.shtml

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