From: P729 (p729@cox.net)
Date: Mon Feb 02 2004 - 20:39:32 GMT-3
Please see inline...
Regards,
Mas Kato
https://ecardfile.com/id/mkato
----- Original Message -----
From: <Danny.Andaluz@triaton-na.com>
To: <ccielab@groupstudy.com>
Sent: Monday, February 02, 2004 9:37 AM
Subject: 802.1q native vlan/router-on-a-stick
> Hello, Group.
>
> What exactly is the native vlan used for?
>
> I've done practice scenarios where the native vlan is required to be
> specified and others where this is not needed. Both ways work. So what
> exactly is the purpose of the native vlan in 802.1q?
The native VLAN's frames are untagged on a trunk.
Caveat: IIRC, some old Catalyst 5000 documentation describes the native VLAN
as the VLAN the port belongs to when it is not trunking. With newer
Catalyst switches, you need to distinguish between trunking and non-trunking
modes. When trunking, the 'switchport trunk native vlan' specifies which
VLAN is untagged while in trunking mode. When not trunking, obviously all
frames are untagged, but their VLAN membership is determined by the
'switchport access vlan' command.
>
> For example, one setup would be where a router is routing for vlans 45 and
> 34 and vlan 45 is configured as the native vlan on the router
sub-interface
> and the switchport. What is the difference between vlan 45 and vlan 34 in
> this case? What traffic, if any, is sent on vlan 45 that is not sent on
> vlan 34?
VLAN 45's frames would be plain-old untagged Ethernet frames on the trunk,
while VLAN 34's frames would be tagged as belonging to VLAN 34.
>
> Using the same scenario, I specify no native vlan on either interface and
> traffic is still routed by the router for both VLANs.
In this case, frames for both VLANs would be tagged on the trunk.
>
> I tried to find an RFC for 802.1q and no luck. The Doc CD doesn't really
> clear this up either.
802.1Q is an IEEE standard. Check out
http://standards.ieee.org/getieee802/download/802.1Q-2003.pdf
>
> Thanks,
> Danny
>
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