From: Hiro Eiji (hpnkpn103@yahoo.co.jp)
Date: Tue Feb 21 2006 - 12:48:36 GMT-3
Hello,
It turns out that there was no such command configured on the
Cat 3550 and still the frames were tagged.
Could anyone shed some light on this?
Thank you,
Hiro
----- Original Message -----
From: "Hiro Eiji" <hpnkpn103@yahoo.co.jp>
To: "Erick Bergquist" <ebergquist@ameritech.net>; <ccielab@groupstudy.com>
Sent: Sunday, February 19, 2006 7:57 AM
Subject: Re: Are native vlan packets really untagged?
> Hi Erick,
>
> Thanks very much for the quick response.
>
> I do not believe I put that command in the switch.
>
> But I dont have the equipment with me right at this moment.
> I will check that out and let you know.
>
> Thanks,
> Hiro
>
> ----- Original Message -----
> From: "Erick Bergquist" <ebergquist@ameritech.net>
> To: "Hiro Eiji" <hpnkpn103@yahoo.co.jp>; <ccielab@groupstudy.com>
> Sent: Sunday, February 19, 2006 3:51 AM
> Subject: Re: Are native vlan packets really untagged?
>
>
>> Do you have the global command configured below?
>>
>> vlan dot1q tag native
>>
>> Use the vlan dot1q tag native global configuration
>> command to enable tagging of native VLAN frames on all
>> IEEE 802.1Q trunk ports. Use the no form of this
>> command to return to the default setting.
>>
>> vlan dot1q tag native
>>
>> no vlan dot1q tag native
>>
>>
>> --- Hiro Eiji <hpnkpn103@yahoo.co.jp> wrote:
>>
>>> Hi,
>>>
>>> I have a question about how native vlan works on
>>> cisco catalyst switches.
>>>
>>> My understanding about native vlan was that the
>>> native vlan packets are
>>> always sent untagged on the 802.1Q trunk link.
>>>
>>> I had a chance to capture native vlan packets on a
>>> 802.1Q trunk link the
>>> other day.
>>> To my surprise, the captured data showed the result
>>> otherwise.
>>> The native vlan packets were in fact tagged with the
>>> native vlan ID.
>>>
>>> Here is the topology that I used.
>>>
>>> Cat3550 - Damn Hub - Cat3550
>>> |
>>> My PC
>>>
>>> When I changed the native vlan ID to 50 at both
>>> ends, the native vlan
>>> packets were tagged with vlan ID 50.
>>>
>>> Those native tagged vlan packets included the STP
>>> BPDUs, CDP frames
>>> and ICMP packets between native vlan segments.
>>>
>>> Has anyone experienced similar phenomena or have any
>>> idea why those native
>>> vlan packets are tagged?
>>> Or if someone could possibly run a quick test on the
>>> equipment and see if
>>> native vlan packets are tagged,
>>> that would be highly appreciated. ( and if you do,
>>> pls make sure you use
>>> non-intel NIC to capture the packets.
>>> Otherwise you cannot see the vlan tags ).
>>>
>>> Thanks,
>>>
>>> Hiro Eiji
>>>
>>>
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