Re: Native vlan from router to switch

only seems to block the broken one as far as I can tell Narbik.

  Port 15 (FastEthernet0/13) of VLAN0020 is broken (Port VLAN ID Mismatch)
    Port path cost 19, Port priority 128, Port Identifier 128.15.
    Designated root has priority 32788, address 000a.b8b3.1e80
    Designated bridge has priority 32788, address 000a.b8b3.1e80
    Designated port id is 128.15, designated path cost 0
    Timers: message age 0, forward delay 14, hold 0
    Number of transitions to forwarding state: 0
    Link type is point-to-point by default
    BPDU: sent 27, received 0

Port 15 (FastEthernet0/13) of VLAN0030 is designated forwarding
    Port path cost 19, Port priority 128, Port Identifier 128.15.
    Designated root has priority 32798, address 000a.b8b3.1e80
    Designated bridge has priority 32798, address 000a.b8b3.1e80
    Designated port id is 128.15, designated path cost 0
    Timers: message age 0, forward delay 0, hold 0
    Number of transitions to forwarding state: 1
    Link type is point-to-point by default
    BPDU: sent 31, received 1

On 08/12/2011 17:22, Narbik Kocharians wrote:
> Spanning-tree will block traffic for every VLAN.
>
> On Thu, Dec 8, 2011 at 8:58 AM, Carlos G Mendioroz<tron_at_huapi.ba.ar> 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:
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>>> >> Blogs and organic groups at http://www.ccie.net
>>> >>
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>>> >
>>> > --
>>> > 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
>>>
>>>
>> --
>> Carlos G Mendioroz<tron_at_huapi.ba.ar> LW7 EQI Argentina

Blogs and organic groups at http://www.ccie.net
Received on Thu Dec 08 2011 - 17:51:33 ART