From: P729 (p729@cox.net)
Date: Sun Oct 06 2002 - 23:15:05 GMT-3
"This would also mean that it is restricted to the native vlan then right?
Without a tag it could not be forwarded to any other vlan."
The tagging mechanism is simply for differentiating traffic belonging to
different VLANs across a given trunk. All VLANs can be tagged, while a
maximum of one can be untagged. The untagged traffic is plain-old Ethernet
traffic--there is nothing distinguishing about it. Only the switches making
up the endpoints of the trunk give significance to the untagged traffic and
assign it to the VLAN designated as the "native VLAN." The traffic for each
VLAN is switched normally, regardless of whether the traffic was tagged or
untagged across the trunk. All that matters is the switch can differentiate
between the different VLANs on the trunk.
That being said, there are other things to ponder. Since VLAN 1 is
well-known as the default VLAN, there could be security implications for
hosts left in this VLAN, such as one-way DoS attacks. Certain switches, such
as the Catalyst 4000, process switch untagged traffic, causing additional
overhead (I'm sure there are others).
Regards,
Mas Kato
https://ecardfile.com/id/mkato
----- Original Message -----
From: "Chris" <clarson52@comcast.net>
To: "P729" <p729@cox.net>; "chenyan" <chenyan@deeptht.com.cn>; "ccielab"
<ccielab@groupstudy.com>
Sent: Sunday, October 06, 2002 12:12 PM
Subject: Re: 802.1q native vlan
I have been looking through the Docs and indeed it does say that native
vlan traffic is not tagged. I guess I have missed that when reading the
switching docs previously, and was always taught that all traffic is tagged.
Thanks for the clarification.
This would also mean that it is restricted to the native vlan then right?
Without a tag it could not be forwarded to any other vlan.
----- Original Message -----
From: "P729" <p729@cox.net>
To: "Chris" <clarson52@comcast.net>; "chenyan" <chenyan@deeptht.com.cn>;
"ccielab" <ccielab@groupstudy.com>
Sent: Sunday, October 06, 2002 2:05 PM
Subject: Re: 802.1q native vlan
> "Any untagged frames will get tagged..."
>
> Mmmm...sounds kinda contradictory doesn't it? Actually, frames assigned to
> the native VLAN of the trunk are sent untagged across the trunk, period.
But
> one might ask, "how would the switches on each end know when there's a
> native VLAN mismatch?" The answer for Cisco switches is through CDP. If
CDP
> is disabled or not available, then they wouldn't know and you can pretty
> much bridge the two VLANs together and maybe not know it...
>
> Regards,
>
> Mas Kato
> https://ecardfile.com/id/mkato
> ----- Original Message -----
> From: "Chris" <clarson52@comcast.net>
> To: "chenyan" <chenyan@deeptht.com.cn>; "ccielab" <ccielab@groupstudy.com>
> Sent: Sunday, October 06, 2002 9:48 AM
> Subject: Re: 802.1q native vlan
>
>
> Any untagged frames will get tagged to the native vlan and travel the
native
> vlan.
>
>
> ----- Original Message -----
> From: "chenyan" <chenyan@deeptht.com.cn>
> To: "ccielab" <ccielab@groupstudy.com>
> Sent: Sunday, October 06, 2002 11:13 AM
> Subject: 802.1q native vlan
>
>
> > hi,guys
> >
> > I want to know why there is native vlan for 802.1q and what is that for?
> >
> > Thanks
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