Unanswered Question
Apr 5th, 2009

Hi All,

can anyone explain the nature of the below error and how it can be fixed ?



*Apr 3 21:31:03.069 UTC: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on GigabitEthernet4/6 (642), with router1 GigabitEthernet4/7 (643).

I have this problem too.
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Marwan ALshawi Sun, 04/05/2009 - 03:17

this is because on the native vlan on the trunk between your switch or router mismatching

the defautl native vlan is vlan1

if you have it diffrent make sure you keep it the same on the both side of trunks

if helps rate

good luck

jeansamarani Sun, 04/05/2009 - 03:33


thanks for you quick reply,

however, the port is configured in access mode. does it make sense?

how to check the native vlan configured in this case?

Giuseppe Larosa Sun, 04/05/2009 - 05:51

Hello Jean,

the two ports are access ports in two different vlans in your case.

Be aware that you have joined two broadcast domains in this way

check with sh run int typex/y if one has a line like

switchport access vlan y

Hope to help


crow930us Sun, 04/05/2009 - 07:57

This message appears on the switch because the configured native VLAN on the port is different than the native VLAN on the connecting switch/router port.

Ensure that the native VLAN for an 802.1Q trunk is the same on both ends of the trunk link. If the native VLAN on one end of the trunk is different from the native VLAN on the other end, the traffic of the native VLANs on both sides cannot transmit correctly on the trunk. This problem can imply some connectivity issues in your network.

Issue the show trunk mod/port command in order to verify the native VLAN that is configured on your switch. In this command, mod/port is the trunk port.


glen.grant Sun, 04/05/2009 - 08:59

If you are sure both ends are in access mode then you have bridged both those vlans together and this can cause all kinds of problems . Once you have determined if that is true or not I would shut that link down .

cameron.moody Sun, 04/05/2009 - 19:38

When you say they are "access ports" - have they actually been hard-coded as access or left as dynamic-desirable and "should" be access ports?

Have you done a "show interfaces trunk" on both devices to confirm the native vlan?

Leo Laohoo Sun, 04/05/2009 - 20:38

Hi Jean,

Try this:

vlan 643


interface GigabitEthernet4/6

switchport trunk native vlan 643


This should fix your VLAN mistmatch


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