NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered

[mccmhtac1]

I know this error is no affecting functionality, but I would like to resolve if possible.

I have three sites connected as follows:

Site A - HQ

6509 with CATOS (switch)and IOS (MSFC)

on MFSC

int vlan 200

ip address 10.10.10.1 255.255.255.248

on SWITCH

set vlan 200 7/37

SIte B - 2600 Router

Int FA0/0

Ip address 10.10.10.2 255.255.255.248

No vlans configured except Vlan 1 (no assigned IP though)

Site C - 3560 layer 2/3 switch

Int Vlan 1

ip address 10.10.10.3 255.255.255.249

All three device and thier respective LANS interact perfectly via Static Routing

Any help will be appreciated,

[Jon Marshall]

Brian

Either make Site A use vlan 1 or make Site C use vlan 200 for the connection.

Jon

[mccmhtac1]

If I changed site A the 6509 to: set vlan 1 7/37

Then it breaks the communications. The switch cannot ping 10.10.10.1 and

the MSFC no longer can access site a or b

[Reza Sharifi]

You changed the switch side but not the MSFC IP to vlan 1

int vlan 200

no ip address

int vlan 1

ip address 10.10.10.1 255.255.255.248

HTH

[Jon Marshall]

Brian

Sorry, i should have been more precise.

The reason it breaks on the 6500 is your IP address is assigned to vlan 200 and the L3 vlan interface on the MSFC for vlan 200 has the IP address in that subnet. So simply changing the port to vlan 1 will not work.

Basically if you have connected these devices together using the same IP subnet then you really need to use the same vlan for that subnet on your L3 switches. 

The easiest thing to do i would have thought, although you need to clarify, is to change the 3560 switch and instead of using vlan 1 use vlan 200.

Alternatively you can simply make the 3560 a routed port instead of assigning it to a vlan. This is the preferred way to do this on all your L3 switches but unfortunately with a 6500 running CatOS and IOS you cannot have routed ports, there is no such thing.

If the only devices in this subnet are the 3 devices you have mentioned in the original post you can either -

1) use vlan 200 and not vlan 1 on the 3560

or

2) configure the port that connects to the 3560 as -

int gi

no switchport

ip address 10.10.10.3 255.255.255.248

However, and this is important, if you have other devices in that subnet that are connected to the switches then you cannot use 2) as above. You need to use the vlan 200 solution.

If you are unclear as to anything i've written please come back for clarification.

Jon

[mccmhtac1]

Jon,

Ok I think you hit it on the head.

There are 3 devices on the subnet, 6509, 2621, and 3560.

I was going to connect these with dot1q trunking, but decided layer 3

was much simpler and easier.

6509 - MSFC: int vlan 200 Ip address 10.10.10.1 /29

2600 - (there is no virtual Vlans configured) int fa0/0 ip address

10.10.10.2 255.255.255.248

3560 - sh vlan - displays vlan 1 as the default, the also shows all the

vlans configured on the 6509.

interface Vlan1 ip address 10.10.10.3 255.255.255.248

so, my question is how do I switch from vlan 1 to vlan 200 on the 3560?

Do I configre int vlan 200, assign it

10.10.10.3 / 29 then put the int GigE 0/24 in it? (GigE is the

interface connected to the 6509 and 2600)

Thank for your time

[Jon Marshall · Accepted solution]

Brian

Yes you can do that but also if there are only 3 devices on that subnet you could do -

int gi0/24

no switchport

ip address 10.10.10.3 255.255.255.248

this way there is no vlan information being exchanged from the 3560 to the 6500 because it is a routed port. This should work fine.

Alternatively you do as suggested, configure vlan 200 on the 3560, create a L3 interface for it and assign the IP there.

Jon

[mccmhtac1]

Thank you very much.

I removed the vlan 1 config on the 3560

and did exactly as you stated.

Because the 6509 is not using eigrp and mostly static routing, I had to

add static routes and all worked fine. The 2600 does use eigrp.

Now I just need to config the 3560 for Voip traffic!

Thank you