Re: Trunking question 'switchport trunk allowed vlan'

From: ALL From_NJ (all.from.nj@gmail.com)
Date: Tue Feb 03 2009 - 21:18:29 ARST

Hello Team,

Interesting topic, since I am currently on the topic of switching in my
studies, I decided to run a quick test with a trunk link.

1)
I configured a trunk and allowed all vlans except vlan 1. I did not change
the native vlan to anything else.
CDP, VTP, etc ... everything works fine like this, no worries about any of
the control traffic. Interesting ... vlan 1 is still listed as the native
vlan in the outputs even though it is not 'allowed'.

I changed the native vlan and everything works fine as we would expect it
to. All good.

2)
I changed back the native vlan to 1. I then added two devices on vlan 1 on
the far sides of the trunk link off of both switches, and also as expected
L3 traffic can not get through since the vlan is not allowed.

Any suggestions for additional 'learning-tests'? Thanks Jason and others
for the questions and discussions ...

~~~~~~~~~~~~~~~~~~~~~~~~~~

On Tue, Feb 3, 2009 at 2:21 PM, Jason Morris <mcnever@gmail.com> wrote:

> well if your native vlan is 50 and its passing the control traffic over
> vlan
> 1 the control traffic would be tagged as vlan 1.
>
> i think by definition if its untagged and your native vlan is 50, its
> passed
> as vlan 50. No functional difference, but just the type of nuance I'd
> expect to get dinged on.
>
>
>
>
>
> On Tue, Feb 3, 2009 at 11:36 AM, Sadiq Yakasai <sadiqtanko@gmail.com>
> wrote:
>
> > Thanks for keeping us honest!
> >
> > But looking closely on this, whats the difference between the Native VLAN
> > frames and those on VLAN 1 (the control traffic) since they are all
> > untagged?
>
>
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-- 
Andrew Lee Lissitz
all.from.nj@gmail.com

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