RE: Re: Vlan dot1q tag Native

From: Scott M Vermillion (scott_ccie_list@it-ag.com)
Date: Wed Oct 22 2008 - 18:27:34 ARST


Hey Reza,

Here is the interface config from the little lab test I just posted
(should've included this output to begin with):

SW1#sh run int fa0/7
Building configuration...

Current configuration : 94 bytes
!
interface FastEthernet0/7
 switchport trunk encapsulation dot1q
 switchport mode trunk
end

So at least with my version of code and my hardware platform, 'switchport
nonegotiate' wasn't necessary (and that kind of makes sense if you think
about it - as long as both ends are hard-coded for 'mode trunk' there
shouldn't be any issues whether 'nonegotiate' is configured or not).

SW1#sh ver | inc image
System image file is
"flash:c3560-advipservicesk9-mz.122-40.SE/c3560-advipservicesk9-mz.122-40.SE
.bin"

Cheers,

Scott

-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of Reza
Toghraee
Sent: Wednesday, October 22, 2008 1:06 PM
To: mihai.grigore@onlinehome.de; ccielab@groupstudy.com
Subject: RE: Re: Vlan dot1q tag Native

Mihai,

I did this long time ago.
It will work if :
1) disable DTP, trunks must be ON, and on no negotiate
2) disable spanning-tree

I don't remember exactly about spanning tree, but I think you must remove
the instance for both native vlans on both switches.

Reza

-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
mihai.grigore@onlinehome.de
Sent: Wednesday, October 22, 2008 10:47 PM
To: ccielab@groupstudy.com
Subject: Re: Re: Vlan dot1q tag Native

Guys,

GREAT EXPLANATION !! Worth much more than the one in DOCCD... I read that
one
several times but did not get it... Now, I feel better about the native
vlan.

I have a question though: is it possible to configure different native VLANs
on
the ends of a trunk between Cisco switches ?

As far as I could see in the lab, as soon as I configure one end, the trunk
is
brought down and an error message pops up, something like: "native VLAN
mismatch... bringing down the trunk".
After I configure the SAME native vlan on the other end of the trunk, this
comes up. As far as I know, this is transmitted via CDP.

I guess scenario 3 does not work with Cisco switches. Maybe between Cisco
and
non-Cisco or between non-Ciscos...

TIA, Mihai

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