Native VLAN Mismatch & BPDUFilter

[Hamza DEHAL]

Hello,

In a client campus network there are two switches connected via a trunk link with a different native vlan:

(SW1 with native vlan 7 and SW2 with native vlan 1),

By looking at the logs, there isn't any native vlan mismatch log, in the interfaces I found that interface on SW2 (with NV: 1) which is connected to SW1 (NV:7) contains the following command "spanning-tree bpdufilter enable".

I deleted this command and these messages started appearing in both switches:

%CDP-4-NATIVE_VLAN_MISMATCH

%SPANTREE-2-BLOCK_PVID_LOCAL

- As far as I know, BPDU Filter is used to stop an interface from generation BPDUs (for some STP puspose)

- Can anyone explain to me how does BPDU Filter prevent a native VLAN mistamch from happening ??

Any help would be much appreciated

Thank you all

[balaji.bandi]

check this may give some examples :

https://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/24063-pvid-inconsistency-24063.html

[MHM Cisco World]

OK, 
config the trunk with disable DTP prevent the both SW to detect native VLAN mismatch because the DTP will inform other SW about native VLAN it use. 
BUT 
STP also do the same 
config the port with prevent it to send BPDU make both SW no detect the native VLAN mismatch.
NOW your case disable STP and DTP so the mismatch not detect 
after enable STP in port immediately SW detect mismatch. 

[Hamza DEHAL]

@MHM Cisco World As I understand from your reply, the command "Spanning-tree bpdufilter enable" doesn't prevent the mismatch, So the mismatch is still happening but the switches can't detect it right ?

[balaji.bandi]

Is there any reason you need different native vlan each switch (best practice you should configure the same Native VLAN on the both side of a Trunk), if not i suggest to match native vlan to get rid of this error.

or that is the requirement try below :

interface Gi t0/1   <<-- change the trunk interface as per the environemtn

switchport trunk native vlan XXXX

switchport mode trunk

no cdp enable

[MHM Cisco World]

Yes you are right, SW detect mismatch either through DTP or STP, and both you disabled

[paul driver]

Hello

---

@Hamza DEHAL wrote:

I deleted this command and these messages started appearing in both switches:

%CDP-4-NATIVE_VLAN_MISMATCH

%SPANTREE-2-BLOCK_PVID_LOCAL

---

Disbale cdp on the nterfaces

int x/x
no cdp enable

[Martin L]

Very strange indeed; what about CDP ? 

is this real gear or virtual lab like CML ?  Although they are getting better, I would not trust any virtual IOS like IOL or IOLv2 from CML.

Regards, ML
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[Hamza DEHAL]

@Martin L it is not a lab, it is real gear