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Access port with Trunk

Unanswered Question
May 15th, 2006
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Hi guys,


If you have a port configured with both:


switchport access vlan x &

switchport mode trunk,


Does the port operate in static access vlan or trunk or both. Please clearify.



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a.giorgi Mon, 05/15/2006 - 04:58
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Hi:


A port can be a tagged (trunk) and untagged (access) at the same time.

The untagged vlan is called native vlan.

When the frame came to the port without vlan id then it is associated with the untagged vlan (1 by default)

When the frame came with vlan id the switch check the port belong to the same vlan.


Hope this help. Please rate if it does.


Regards


Alberto Giorgi from spain.

kelvin-yeo Mon, 05/15/2006 - 05:26
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Hi there,


Thanks.


I understand what you mmeant here.


interface FastEthernet0/23

switchport access vlan 101

switchport trunk encapsulation dot1q

switchport trunk native vlan 101

switchport mode trunk


Above, what will " switchport access vlan 101" meant?


Cheers

amit-singh Mon, 05/15/2006 - 05:04
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Hi.


looking at your present config if its a switch which support dot1q only, it will work on trunk not a static vlan port. On the other switches which has the ISL trunk support, it will work as a static access port until u define the encapsulation for the port.


A port can work both as a tagged and untagged for a vlan as explained by the poster above.


HTH, Please rate if it does.


-amit singh

ycae Mon, 05/15/2006 - 05:12
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Well i think that this will work without problem but i think i read once that on a security point of view you should always create trunks on unused vlans for example vlan 1. Correct me if i am wrong.


Yves

kelvin-yeo Mon, 05/15/2006 - 05:39
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Hi Again,


If its a uplink between 2 cisco switch,the above cmds put the ports into trunk with native vlan of 101.


Then how will the ' switchport access vlan 101' play apart in this case. Is it ignored?


Thanks

amit-singh Mon, 05/15/2006 - 05:55
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  • Blue, 1500 points or more

Hi,


' switchport access vlan 101' will be ignored if this command is given before trunk command. But if it is given after the trunk command then it will change the port into an access port.


HTH, Please rate if it does.


-amit singh

kelvin-yeo Mon, 05/15/2006 - 06:04
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amit,


Thats the answer i'm looking for. Thank you.


Is there any writeup on this?


I will rate your post

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