Native Vlan Mismatch

[l.meyer]

Hi,

I have a problem with an unpractical system error message. Has anyone an idea ?

SW 1 Port GE 1/1 is configured with VLAN 66 (no trunking). This Port is connected to SW 2 Port 2/50 which is configured with VLAN 1. I think it´s a standard design to connect access switches to the distribution. But the following error occurs : %CDP-4-NATIVE_VLAN_MISMATCH.

The native VLAN is only used in combination with dot1q trunking, but I don´t use dot1q and so the error (warning) message is absolutely unnecessary. Similarly cdp only checks the "VLAN mismatch" if both switches support dot1q. With an old access switch (CatOS 5.5(16)) in the same configuration the message don´t occur. The sense escapes me. I think cdp should only check "VLAN mismatch" if dot1q is active.

With CatOS I can change the cdp logging level and this message is general disabled. It´s not fine, but work.

With Native IOS I must change the general logging level to "level 3 - ERROR". This is no solution, only a stupid work around !!!

Do anyone understand the purpose of this message or is there another solution ???

[milan.kulik]

Hi,

if you issue sh cdp nei det you'll see CDP is sending native VLAN info even on non-trunking ports. One older native VLAN definition is "the VLAN to which the port returns when trunking stops".

I don't think that connecting VLAN66 port to VLAN1 port is "a standard design to connect access switches to the distribution". VLAN numbers are supposed to be consistent generally.

You are correct regarding the error message workaround.

Just one addditional idea:

CDP ver 1 doesn't send the native VLAN info.

So you can use set cdp version v1 (CatOS) or no cdp advertise-v2 (IOS) without logging changing.

Regards,

Milan

[l.meyer]

Hi Milan,

thanks for your reply.

It´s a high available network with over 800 access switches. For very quick switch replacement we need a standard access switch configuration independent to the access area. Independent from this point VLAN configuration only at the distribution site has many advantages and certainly it´s not the only network with such requirements.

Go back to CDPv1 is an idea, but I think it´s not a solution for the future. The real function of this message is to avoid VLAN mismatches on dot1q trunks. So I think it´s the correct implementation that cdp only checks "native vlan mismatches" on active dot1q trunks.

If I don´t get it completely wrong, than I think it´s the right way to modify this implementation. But it´s certainly difficult to convince the cisco lap.

[wyoun]

this problem occured between sw1 and sw2 vlan mismatch...

I think change sw2 vlan number and vlan name, sw2 vlan 1 --> vlan 66

sw1 and sw2 connect same vlan.

switch is not recommand used default vlan (vlan 1) for end node

vlan 1 is only used for management switch.

bye...

[KAROLY KOHEGYI]

Hi!

We sense the same problem after upgrade from Cat5000 to Cat6500.

I think this is a software problem and can not solve from CLI.

Many people raise this question on this forum and i can't see solution.

If anybody try to open TAC case the cisco maybe solve. ( you can do the upgrade !! )

Best Regards

[wyoun]

If you used Native IOS...

set the sw1

Router(config-if)# switchport trunk native vlan vlan_ID

(Optional) Configures the 802.1Q native VLAN.

When configuring the native VLAN, note the following:

The vlan_ID can be 1 through 4094, except reserved VLANs (see Table 8-1).

The default VLAN is not automatically used as the native VLAN.

Technical document:

http://www.cisco.com/univercd/cc/td/doc/product/lan/cat6000/12111bex/swcg/layer2.htm#78452

bye..good luck...