NATIVE VLAN MISMATCH

mitra.kama · ‎01-07-2010

I am using sw 3560, where im getting notification on log file i.e

"NATIVE_VLAN_MISMATCH: NATIVE VLAN MISMATCH DISCOVERED ON FASTETHERNET0/10 (6), WITH OUTSTATION FASTETHERNET0/15 (4)."

I want to know why it is coming and what will be the consequences if we don't rectify, and

also pse give me suggestion, how to solve this problem..and what is Native VLAN and VLAN

mitra....

Ganesh Hariharan · ‎01-07-2010

Hi Mitra,

The native VLAN is the VLAN that is used if the interface is to become a Layer 2 interface. If you do not explicitly define a native VLAN, VLAN 1 becomes the native VLAN by default. Be aware that an IEEE 802.1Q header is not added when data are sent on the native VLAN. Ensure that the trunk ports on both of the connected devices have the same native VLAN. A mismatch in native VLANs can cause inter-VLAN routing issues, among other problems

As per your error NATIVE_VLAN_MISMATCH: NATIVE VLAN MISMATCH DISCOVERED ON FASTETHERNET0/10 (6), WITH OUTSTATION FASTETHERNET0/15 (4)."

One of the device is having native vlan as 6 and other one with 4 so this is creating these type of messages.

Hope this clear out your query !!

Regards

Ganesh.H

Giuseppe Larosa · ‎01-07-2010

Hello Mitra,

CDP messages for switch ports contain information about in what vlan a port is associated.

The message is telling you that you have joined two broadcast domains : vlan 6 on local node and vlan4 on remote end device.

This can be wanted or it can be the result of incorrect cabling and/or configuration.

native vlan is an 802.1Q concept but in this case means different vlan in the two ports.

if the port is an 802.1Q trunk there are issues because native vlan is the vlan whose frames travel untagged.

Having a different native vlan means the two sides regard untagged frames as belonging to different vlans. This can break IP connectivity.

Hope to help

Giuseppe