Forwarding untagged frame to all vlan configured ports-switch 2960 Catalyst

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Nov 24th, 2008
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Hi All,


I am using switch cisco 2960 catalyst switch, I have created a trunk in that using following commands:


interface FastEthernet0/10

switchport trunk native vlan 20

switchport mode trunk


and one port has been configured for vlan id 20 using 802.1q tags:


interface FastEthernet0/3

switchport access vlan 20

switchport mode access


Using, this i am able to receive both tagged(802.1q) and untagged frame on port 0/3.


But, I want to forward untagged frame to other vlan configured ports as well.


I am using 802.1q tags format.


Pls suggest how i can achieve the same.


Regards,

Prakhar


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Sebastian Helmer Tue, 11/25/2008 - 01:55
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Hello Prakhar,


On Port 0/10 all untagged frames will be in VLAN20, all tagged frames will forwaded depens on the tag.


In Port 0/3 all untagged frames will also be in vlan 20 and because of the mode access settings all other frames will not be handeld.I think droped.


What do you exaclty want to do, I don't really understand the situation you want achive sorry..


best regards

Sebastian

PrakharVig Tue, 11/25/2008 - 05:54
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Hi Sebastian,


I have a situation where, i need to create a trunk, which will be recieving 802.1q tagged data as well as untagged data.


And, I want to forward the 802.1q tagged data to vlan 802.1q configured ports respectively, and in the same time want that all vlan configured ports should also be able to see untagged data.


Regards,

Prakhar

Sebastian Helmer Tue, 11/25/2008 - 07:00
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OK I try to explain maybe this makes it clear for you.


On a trunk Port, you will see all 802.1q tagged frames you allow, per default you will see all vlan's. When you want you can change the native vlan, like you did switchport trunk native vlan 20.

So you can send and receive 802.1q tagged frames. All untagged 802.1q frames will be "go through" vlan 20.


On a access Port you can only send or receive 802.1q untagged frames. The frams from the vlan you configured on that access port.


So I think your configuratio should work. interface 0/10 will send and receive tagged frames and will send untagged frames over vlan 20. on port 0/3 you can send untagged frames and receive all untagged frames from port 0/10.


I'm not sure, but i think you must be sure that if you have more than 1 switch, you must look that the connection between the both, will work over the same native vlan (20 in this case).


hope this helps.


best,

sebastian

PrakharVig Tue, 11/25/2008 - 07:49
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Hi Sebastian,


Thanks for ur response.


Actually,my scenario is like this,I want to create two vlans, data will be coming to port 0/10(both tagged and untagged).


Lets assume, one vlan is at port 0/3(allow only valn id 20) and other is at 0/4 (allow only vlan 30). Now , I want the tagged data with vlan 20 should go to port 0/3, tagged data vlan 30 should go to port 0/4.


And, untagged data should goto both port 0/3 nd port 0/4.


Pls, tell me how can i configure this situation.


For single vlan i am able to do it using configuration I told u earlier.


But for this I am clueless.


Thanks and Regards,

Prakhar

Sebastian Helmer Tue, 11/25/2008 - 11:46
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Hi Prakhar,


I don't really understand wherefore you need this, but this is not the topic ;-)..


This will not work...

You can only use one native vlan per port. so you can't use Port 0/10 "to fetch two untagged vlans"...

You can only use a trunk to "fetch" both tagged vlans frames and ONE native vlan to "fetch" ONE untagged vlan.


So, sorry no chance I think for your task. When you can tell me more details why you need this, maybe we can think together for a solution.



best regards,

Sebastian

PS: I go off now, see you tomorrow

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