From: Bob Sinclair (bsinclair@netmasterclass.net)
Date: Mon Feb 02 2004 - 15:04:16 GMT-3
Danny,
802.1Q is an IEEE standard. It can be downloaded free from the following
link:
http://standards.ieee.org/getieee802/802.1.html
It is critical when using 802.1Q trunks that you are consistent with the
native vlan. When you trunk non-Cisco switches running 802.1Q to Cisco
Switches running PVST+, there is a common spanning tree running on the
native vlan. Native vlan inconsistencies can result in bridging separate
spanning trees together. Here is a link that offers more detail on this
scenario:
http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121newft/121t/121t3/dtbridge.htm
HTH,
Bob Sinclair
CCIE #10427, CISSP, MCSE
www.netmasterclass.net
----- Original Message -----
From: <Danny.Andaluz@triaton-na.com>
To: <ccielab@groupstudy.com>
Sent: Monday, February 02, 2004 12:37 PM
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?
>
> 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?
>
> Using the same scenario, I specify no native vlan on either interface and
> traffic is still routed by the router for both VLANs.
>
> I tried to find an RFC for 802.1q and no luck. The Doc CD doesn't really
> clear this up either.
>
> Thanks,
> Danny
>
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