[e-nsp] Possible to add 1 port as untagged to 2 different VLANs?

[Sander Aerts]

Fredrik,

It is not possible to add a single switch port to 2 vlan's with the 
untagged, this is because vlan tagging add some information to the packets 
that are send acros the network.
The information that is added to the packets are the VLAN-ID in this case, 
if you set a port to tagged the header of a packet will be modified by the 
switch and the vlan ID will be set.
But if you set a port to untagged, the switch doesn't send the information 
with packets, so then it operates as a normal switching port (This is 
required for connecting, for example computer systems or you need to compile 
a linux kernel with vlan tagging support).

But a hub is in fact a stupid device, information send to the hub will be 
transported to every port, so in your scenario if it is not a switching hub 
or something, you can set the extreme port tagged/tagged and
create vlan support on your computer system if you use linux. Then in 
theorie i need to work.

Another point, think that is was possible to add one port to 2 VLAN's with 
the untagged method that will be the same as connecting 2 vlan's to 
eachother.
So that also means, that your VLANS are OBSOLETE and you created a security 
hole :)

--

Regards,

Sander Aerts

----- Original Message ----- 
From: "F J" <ripprapp at hotmail.com>
To: <extreme-nsp at puck.nether.net>
Sent: Wednesday, April 05, 2006 9:27 PM
Subject: Re: [e-nsp] Possible to add 1 port as untagged to 2 different 
VLANs?


> Hi again,
> Of course I meant layer3 ROUTING (not switching) in my last reply :)
>
> The thing is that I do not want to start routing in my Extreme equipement, 
> I
> rather leave that to my Routers...
>
> So, is multinetting something that could solve my problems (being able to
> add a port as untagged to several VLANs but NOT doing any layer3 routing 
> in
> my Sumit48i)?
>
> BR
> /// Fredrik
>
>
>>From: "F J" <ripprapp at hotmail.com>
>>To: extreme-nsp at puck.nether.net
>>Subject: Re: [e-nsp] Possible to add 1 port as untagged to 2 different
>>VLANs?
>>Date: Wed, 05 Apr 2006 20:08:18 +0200
>>
>>Hi,
>>And I can only use Multinetting if I am running layer3 switching in the
>>Summit? Am I correct?
>>BR
>>/// Fredrik
>>
>>
>> >From: "F J" <ripprapp at hotmail.com>
>> >To: extreme-nsp at puck.nether.net
>> >Subject: [e-nsp] Possible to add 1 port as untagged to 2 different 
>> >VLANs?
>> >Date: Wed, 05 Apr 2006 18:14:01 +0200
>> >
>> >Hi,
>> >I have a hub connected to port 17 in my Summit48i running SW7.4. To that
>> >hub
>> >I have connected 2 computers, one on the 192.168.0.0/24 net and the 
>> >other
>> >on
>> >the 172.16.0.0/16 net.
>> >
>> >These two computers are part of two different VLANs configured in the
>> >Summit. Since the hub does not support VLANs I would like to add the
>>Summit
>> >port17 as untagged in both VLANs.
>> >
>> >Is it possible to add 1 port as untagged to 2 different VLANs in the
>> >Summit?
>> >How do I do it?
>> >
>> >I saw something about creating own "protocols", but I mean, in my case
>>both
>> >computers are running standard TCP/IP.
>> >
>> >BR
>> >/// Fredrik
>> >
>> >(I know it's a strange "setup" and this is not really the network setup,
>> >but
>> >it describes exactly what I want to do, even if it's rather weird :) )
>> >
>> >
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>>
>>
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