From: Clay K Auch (clauch) (clauch@cisco.com)
Date: Fri Oct 05 2007 - 15:47:10 ART
Hello Rich,
Not sure if this helps, but if I have an inconsistent native vlan on the other end of my trunk ... The information is provided in the following output as well as notification logging. Notice, the "Native VLAN: 77 (Mismatch)" at almost the very bottom of the output ... Then the mismatch log message below that.
============
SW3#sh cdp nei f0/19 det
-------------------------
Device ID: SW4
Entry address(es):
IP address: 141.1.255.10
Platform: cisco WS-C3560-24PS, Capabilities: Switch IGMP
Interface: FastEthernet0/19, Port ID (outgoing port): FastEthernet0/19
Holdtime : 126 sec
Version :
Cisco IOS Software, C3560 Software (C3560-ADVIPSERVICESK9-M), Version 12.2(35)SE1, RELEASE SOFTWARE (fc1)
Copyright (c) 1986-2006 by Cisco Systems, Inc.
Compiled Tue 19-Dec-06 10:54 by antonino
advertisement version: 2
Protocol Hello: OUI=0x00000C, Protocol ID=0x0112; payload len=27, value=00000000FFFFFFFF010221FF0000000000000018BA598C00FF0000
VTP Management Domain: 'IE'
Native VLAN: 77 (Mismatch)
Duplex: full
Management address(es):
IP address: 141.1.255.10
SW3#
02:24:59: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on FastEthernet0/19 (255), with SW4 FastEthernet0/19 (77).
======
Clay
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of Rich Collins
Sent: Wednesday, October 03, 2007 4:45 PM
To: Joseph Saad
Cc: chidambaram sakthivel; ccielab@groupstudy.com
Subject: Re: 3550 why does vlan int go down
Only the same topic I had a similar question. How do you know if the native VLAN is correctly configured on both sides of a static dot1q trunk? For example you have no access to the other side. I had this case once with a 3rd party switch.
On the Cisco side the "show int trunk" looked fine and I also believe the "sh int gi 0/x switchport" also looked fine but the native vlan was mismatched. Is there some "show command" or what would a good debug for this.
Rich
On 10/3/07, Joseph Saad <joseph.samir.saad@gmail.com> wrote:
>
> That is more of a generalization.
>
> More precisely, the native VLAN is configured per trunk port, and the
> requirement is to have the native vlan consistent at the 2 ends of
> each trunk port rather than on all ports of the switch.
>
> Joseph.
>
> On 10/3/07, chidambaram sakthivel <sakthivelc@indiainfo.com> wrote:
> >
> > Hi Navid,
> >
> > I feel that both the switches should be configured for same native
> > Vlan either 1 or 2.
> > Because the untagged frames from sw1 Vlan1 will be forwarded to
> > Vlan2 of sw2, it will create problems what you observe now.
> >
> > In Dot1Q encapsulation the native Vlan should be configured same on
> > the switches.
> >
> > Thanks,
> > Sakthivel.C
> >
> > > ----- Original Message -----
> > > From: xdsgrrr <xdsgrrr@consultcommerce.com>
> > > To: ccielab@groupstudy.com
> > > Subject: Re: 3550 why does vlan int go down
> > > Date: Tue, 02 Oct 2007 10:58:16 +0300
> > >
> > >
> > > Check with show interface trunk and see that evrything is ok with
> > > vlan
> > > 1 :)) and use show spanning-tree vlan 1 br to verify that port is
> > > in forwarding state for this vlan br, Atanas Yankov On Tue,
> > > 2007-09-25 at 11:26 +0200, Navid Daghighi wrote:
> > > > Hi,
> > > >
> > > > In this simple example, where I configured a mismatch native vlan :
> > > >
> > > > sw 1 : dot1Q, native vlan = 1
> > > > sw 2 : dot1Q, native vlan = 2
> > > >
> > > > SH IP INT BRIEF shows that :
> > > > fa0/x stays up/up
> > > > vlan1 goes up/down
> > > >
> > > > What is the logic behind this behavior ?
> > > > I would have expected the fa0/x to go up/down !
> > > >
> > > > Thanks,
> > > > Navid
> > > >
> > > >
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