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Community Member

Native VLAN mismatch error on 4006 switch

A 4006 switch is connected to a 5500 switch and the following error message keeps coming every 5 minutes.The Native VLAN settings are correct.We have set cdp disable command on the switch also.

%CDP-4-NVLANMISMATCH:Native vlan mismatch

detected on port 1/1 .

Any thoughts.

-Thanks.

10 REPLIES
Purple

Re: Native VLAN mismatch error on 4006 switch

Make sure the ports that connect the two switches are set to the same vlan , if one is set to say vlan 10 then the other end must be set to vlan 10 .

Community Member

Re: Native VLAN mismatch error on 4006 switch

I have the same problem with 3550-48 keep getting this message on 6513

%CDP-4-NVLANMISMATCH:Native vlan mismatch detected on port 2/2

Can I change default name VLAN1 on 3550-48 to mach the port VLAN name on 6513?

by the way I don't have this problem with cisco 3548-48 All 3548 switches in deferent VLAN they have the same default name

Thanks

Community Member

Re: Native VLAN mismatch error on 4006 switch

Is this connection a trunk? If so, make sure that the configurations on both sides are the same for the ports that are connected. Two switches connected with a trunk, the trunk has same configuration on both sides. However, the native vlan is set at the port level. So the actual port {set port 1/1 10} should be the same on both sides, also should be a VLAN in the trunk.

VLANs are switch specific and should not create this message in a non-trunk environment, this is one of cisco's little 'undocumented features' i am not sure how to turn the message off, but it does not hurt anything.

Disabling cdp does nothing for this issue though.

Re: Native VLAN mismatch error on 4006 switch

I've seen the same message on Cat4000 on non-trunk port.

If you connect two switches via ports which are assigned to different VLANs (let's say VLAN4 on Cat3548 and VLAN1 on Cat4006) you receive this message to syslog on Cat4000.

The reason is that CDP is notifying the other switch about native VLAN of the port and in the case of non-trunk port the native VLAN is considered to be the VLAN to which the port has been assigned.

You can check this via "sh cdp nei" command on Cat4000. If you see a "*" following port ID in the line describing a neighbour it indicates this problem.

Also using "sh cdp nei det" will show you a Native VLAN: 4 (Mismatch).

If you have to leave different VLAN assignment on both line ends you can stop the error messages going to syslog by

set logging level cdp 3 default

on your Cat4000.

Regards,

Milan

Community Member

Re: Native VLAN mismatch error on 4006 switch

I'm assuming that you're using the interface as a trunked port. To solve the problem:

1. Disable the interface (on both switches) - set port disable ...

2. Turn off trunking (on both switches) - clear trunk ...

3. Verify that the interfaces are now back to their original VLAN - show port ... -> make sure that the VLAN matches (on both switches). If not matched then simply set vlan X ...

4. Re-enable trunking on the interfaces (on both switches).

5. Re-enable the interfaces (on both switches).

Let me know if this doesn't work.

Bronze

Re: Native VLAN mismatch error on 4006 switch

Hi,

when the configuration is okay and you has different vlans on the catalyst you can switch off cdp.

Then you don't become the messages.

Regards

Peter

Community Member

Re: Native VLAN mismatch error on 4006 switch

All you need to do is modify the port assignment form VLAN 1 (Default) to whatever the other swith port VLAN X it connects to, so that both end ports are assigned/part of the same VLAN #.

for example to change port 2/1 from VLAN 1 ( default VLAN) to VLAN 4

Do following:

set vlan 4 2/1

so port 2/1 will be modified and to new VLAN 4 (instead of vlan 1)

to match the other end switch VLAN for a port.

Community Member

Re: Native VLAN mismatch error on 4006 switch

The set vlan command should be Ok on the 5000. For the 4006, issue the following command on the port that you are trunking:

switchport trunk native vlan ###

- where number is the vlan number specified on the 5000.

Hope this helps.

Community Member

Re: Native VLAN mismatch error on 4006 switch

here is what I have

CISCO 6513 has 10 vlans one for each floor

CISCO 3550 SMI on some floors connecting to the main switch CISCO 6513 with fiber (GBIC)

Some Floors has CISCO 3548

let's say

CISCO 6513 port 1/1 VLAN101 connecting to 10th Floor closet has CISCO 3550-48 SMI with fiber

CISCO 6513 port 1/2 VLAN 111 connecting to 11th Floor closet has CISCO 3548 with fiber

Now only the ports connecting to 3550 SMI keep getting this message

%CDP-4-NVLANMISMATCH:Native vlan mismatch detected on port 1/1

Both 3538 & 3550 configured as the same

I tried to change and the default VLAN1or create new int on 3550 SMI to mach the one on 6313 but it didn't help

Any idea? Thanks

Community Member

Re: Native VLAN mismatch error on 4006 switch

FYI... Native Vlan Mismatch should be fixed. There are ramifications... and if you are not careful the results could impact your general network performance and hinder proper support.

802.1q Native VLAN Consideration

802.1q trunking inserts a four-byte 802.1q tag field into frames sent over the trunk, which contain VLAN information. The 802.1q tag is inserted into each frame transferred over the trunk except for frames transmitted on the native VLAN, which are sent untagged. In most cases, the native VLAN has to match on both sides of the trunk unless there is a specific unusual configuration requirement, which is outside the scope of this document. If the native VLANs do not match, the switch will log Cisco Discovery Protocol (CDP) messages stating the mismatch. While not catastrophic, this setup effectively causes the two different native VLANs to be merged into one larger L2 broadcast domain (VLAN). These two VLANs will attempt to calculate one common Spanning-Tree Protocol (STP) topology for such bridged native VLANs, with the risk of eventually exceeding the maximum supported STP diameter

Here is the link for the whole doc...

http://www.cisco.com/en/US/partner/tech/tk389/tk213/technologies_configuration_example09186a0080094bc5.shtml

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