From: Hiro Eiji (hpnkpn103@yahoo.co.jp)
Date: Sat Feb 18 2006 - 19:57:07 GMT-3
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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