Re: Native vlan from router to switch

Yes, you are correct, you can get around it, i was referring to the default
behavior.

On Thu, Dec 8, 2011 at 9:23 AM, Paul Cocker <paul.cocker_at_gmx.com> wrote:

> Spanning-tree...
>
> I'm guessing the vlan is in the bpdu.
>
> with this config...
>
> SW1
> interface FastEthernet0/13
> switchport trunk encapsulation dot1q
> switchport trunk native vlan 10
> switchport mode trunk
> switchport nonegotiate
>
> SW2
> interface FastEthernet0/13
> switchport access vlan 20
> switchport trunk encapsulation dot1q
> switchport trunk native vlan 20
> switchport mode trunk
> switchport nonegotiate
> no cdp enable
>
>
> you get this...
>
> *Mar 1 00:18:26.994: %SPANTREE-2-RECV_PVID_ERR: Received BPDU with
> inconsistent peer vlan id 10 on FastEthernet0/13 VLAN20.
> *Mar 1 00:18:26.994: %SPANTREE-2-BLOCK_PVID_LOCAL: Blocking
> FastEthernet0/13 on VLAN0020. Inconsistent local vlan.
>
> You can disable spanning tree, or use bpdufilter to get around it.
>
>
> On 08/12/2011 16:58, Carlos G Mendioroz wrote:
>
>> What mechanism is responsible for such blocking ?
>>
>> -Carlos
>>
>> Narbik Kocharians @ 08/12/2011 13:34 -0300 dixit:
>>
>>> Between any two switch if the Native VLAN is mismatched the trunk will
>>> come up but you won't be able to pass any traffic through it, and you can
>>> see that with a "Show spanning block".
>>> On Thu, Dec 8, 2011 at 4:31 AM, David Bass <davidbass570_at_gmail.com<mailto:
>>> davidbass570_at_gmail.com**>> wrote:
>>>
>>> We are talking about CCIE lab, so best practice and "working" status
>>> all go out the window :). In his scenario he's talking about router
>>> to switch trunk, so no VTP or STP (if you do this switch to switch
>>> you'll definitely have issues though, so very good to know)...CDP
>>> will definitely bark non-stop though which is very irritating.
>>>
>>>
>>>
>>> On Dec 8, 2011, at 6:08 AM, Carlos G Mendioroz wrote:
>>>
>>> > May be depending on the equipment, the trunk will "form" just fine,
>>> > if VLAN hopping is not considered to be a problem :)
>>> > CDP may barf. If VLAN 1 is involved, other griefs will pop.
>>> >
>>> > Different problems:
>>> > -framing: no problem, but "native VLAN" frames do not signal
>>> which VLAN
>>> > they belong to, so if they do not match, frames will hop from one
>>> VLAN
>>> > to the other.
>>> >
>>> > -signalling (DTP): AFAIK, VLANs are not part of the info
>>> interchanged, so the trunk will form even if native is not the same.
>>> >
>>> > -control: (CDP/VTP/STP/...): well, you may have a problem here.
>>> > In particular, CDP/VTP go on VLAN 1, so if this is one of the VLANs
>>> > involved in the crossing, it won't work.
>>> >
>>> > -Others ?
>>> >
>>> > -Carlos
>>> >
>>> >
>>> > David Bass @ 08/12/2011 08:25 -0300 dixit:
>>> >> The trunk will come up fine, but you won't have IP connectivity
>>> between the 2 devices on the VLANs/subnets you are expecting because
>>> the 2 native VLANs are being bridged. Do some research on how dot1q
>>> trunks work and you should be able to figure it out. On Dec 7, 2011,
>>> at 11:40 PM, CCIE KID <eliteccie_at_gmail.com
>>> <mailto:eliteccie_at_gmail.com>> wrote:
>>> >>> Hi fellas,
>>> >>>
>>> >>> I tested a scenario where the Native vlan differs from the
>>> router port to
>>> >>> the switch port. I understood that if the NAtive vlan
>>> mismatches on a trunk
>>> >>> port , then appropriate trunking wont be formed.
>>> >>> But when i connect my router to a switch and in the router
>>> subinterface . I
>>> >>> am having a native vlan of 20 and in the switch port it is
>>> having a native
>>> >>> vlan of 10 , but still the trunk is forming perfectly
>>> >>>
>>> >>> Can someone correct me
>>> >>> fa0/1.1 fa0/1
>>> >>> Router1-----------------------**------------------------Switch 1
>>> >>>
>>> >>> Router 1
>>> >>>
>>> >>> inter fa 0/1.1
>>> >>> encap dot1q 20 native
>>> >>> ip add 10.1.1.1 255.255.255.0
>>> >>> no sh
>>> >>>
>>> >>>
>>> >>> Switch 1
>>> >>>
>>> >>> int fa 0/1
>>> >>> enc dot1q 10 native
>>> >>> swi trunk enc dot
>>> >>> swi mo trunk
>>> >>> no sh
>>> >>>
>>> >>>
>>> >>> But s
>>> >>>
>>> >>> --
>>> >>> With Warmest Regards,
>>> >>>
>>> >>> CCIE KID
>>> >>> CCIE#29992 (Security)
>>> >>>
>>> >>>
>>> >>> Blogs and organic groups at http://www.ccie.net
>>> >>>
>>> >>>
>>> ______________________________**______________________________**
>>> ___________
>>> >>> Subscription information may be found at:
>>> http://www.groupstudy.com/**list/CCIELab.html<http://www.groupstudy.com/list/CCIELab.html>
>>> >> Blogs and organic groups at http://www.ccie.net
>>> >>
>>> ______________________________**______________________________**
>>> ___________
>>> >> Subscription information may be found at:
>>> http://www.groupstudy.com/**list/CCIELab.html<http://www.groupstudy.com/list/CCIELab.html>
>>> >
>>> > --
>>> > Carlos G Mendioroz <tron_at_huapi.ba.ar <mailto:tron_at_huapi.ba.ar>>
>>> LW7 EQI Argentina
>>>
>>>
>>> Blogs and organic groups at http://www.ccie.net
>>>
>>> ______________________________**______________________________**
>>> ___________
>>> Subscription information may be found at:
>>> http://www.groupstudy.com/**list/CCIELab.html<http://www.groupstudy.com/list/CCIELab.html>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>> --
>>> *Narbik Kocharians
>>> *CCSI#30832, CCIE# 12410 (R&S, SP, Security)
>>> *www.MicronicsTraining.com* <http://www.micronicstraining.**com/<http://www.micronicstraining.com/>
>>> >
>>> Sr. Technical Instructor
>>> YES! We take Cisco Learning Credits!
>>> Training & Remote Racks available
>>>
>>
>
> Blogs and organic groups at http://www.ccie.net
>
> ______________________________**______________________________**
> ___________
> Subscription information may be found at: http://www.groupstudy.com/**
> list/CCIELab.html <http://www.groupstudy.com/list/CCIELab.html>
>
>
>
>
>
>
>
>

-- 
*Narbik Kocharians
*CCSI#30832, CCIE# 12410 (R&S, SP, Security)
*www.MicronicsTraining.com* <http://www.micronicstraining.com/>
Sr. Technical Instructor
YES! We take Cisco Learning Credits!
Training & Remote Racks available
Blogs and organic groups at http://www.ccie.net