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Bronze

can native vlan 1 be blocked using dot1q/ISL?

hi every body!

I want to know can i block nativa vlan 1 by:

switchport trunk encapsulation dot1q

switchport trunk allowed vlan except 1

or

switchport trunk allowed vlan remove 1

Using ISL:

switchport trunk encapsulation isl

switchport trunk allowed vlan except 1

or

switchport trunk allowed vlan remove 1

thanks!

2 ACCEPTED SOLUTIONS

Accepted Solutions

Re: can native vlan 1 be blocked using dot1q/ISL?

You cant remove native vlan from trunk. However, you can change the native vlan from default of 1 to some other vlan number.

"switchport trunk native vlan x"

Hall of Fame Super Blue

Re: can native vlan 1 be blocked using dot1q/ISL?

Sarah

As already mentioned you can change the native vlan to be something other than vlan 1. The native vlan is simply the vlan that is sent across a trunk without a tag. By default it is vlan 1.

Cisco recommend using a dummy vlan for the native vlan ie. a vlan that is not routed and has no devices connected into it.

If you make the native vlan a vlan other than vlan 1 it is important to note that vlan 1 will still be used to send DTP,VTP,PagP frames which will be tagged.

You can if you want to make sure that the native vlan is tagged by using the command

vlan dot1q tag native

Jon

4 REPLIES

Re: can native vlan 1 be blocked using dot1q/ISL?

You cant remove native vlan from trunk. However, you can change the native vlan from default of 1 to some other vlan number.

"switchport trunk native vlan x"

Bronze

Re: can native vlan 1 be blocked using dot1q/ISL?

thanks for your reply. I applogise for posting multiple instances of same post by mistake.

Have a nice day!

Hall of Fame Super Blue

Re: can native vlan 1 be blocked using dot1q/ISL?

Sarah

As already mentioned you can change the native vlan to be something other than vlan 1. The native vlan is simply the vlan that is sent across a trunk without a tag. By default it is vlan 1.

Cisco recommend using a dummy vlan for the native vlan ie. a vlan that is not routed and has no devices connected into it.

If you make the native vlan a vlan other than vlan 1 it is important to note that vlan 1 will still be used to send DTP,VTP,PagP frames which will be tagged.

You can if you want to make sure that the native vlan is tagged by using the command

vlan dot1q tag native

Jon

Bronze

Re: can native vlan 1 be blocked using dot1q/ISL?

Thanks jon for your reply!

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