NATIVE_VLAN_MISMATCH

[sanjay.khurana]

Hi ,

I have 2 cisco 6509 Switch at my sites. Both switches are connected thru ethernet connection in routing mode. i am getting NATIVE_VLAN_MISMATCH error

following is conf of Switch A

!

interface Vlan987

ip address 10.167.13.249 255.255.255.252

interface GigabitEthernet13/2

no ip address

logging event link-status

logging event trunk-status

switchport

switchport access vlan 987

switchport mode access

end

Switch B

interface Vlan911

ip address 10.167.13.250 255.255.255.252

ip summary-address eigrp 100 0.0.0.0 0.0.0.0 5

no ip mroute-cache

end

interface GigabitEthernet2/0/25

switchport access vlan 911

srr-queue bandwidth share 1 70 25 5

srr-queue bandwidth shape  3  0  0  0

priority-queue out

mls qos trust dscp

snmp ifindex persist

arp timeout 300

end

and following is error log

NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on GigabitEthernet13/2 (987), with  GigabitEthernet2/0/25 (911)

as per my knowledge when we have trunk between switches and using switchport trunk native vlan command on both side and vlan id is not same then this type of error is genrate by switch. as of now i don't have trunk between switches then why i am getting this error not understand.

Note : no any other port are member of vlan.

no any another connection between switches.

[jonathanaxford]

Hi,

Are the switches connected together via the ports you have described above? If so, you will have a native VLAN mismatch as far as CDP is concerned as each port is in a different VLAN.

One side of the link is in VLAN 987 and one side is in 911. I have a feeling that if CDP is running between the switches is will be detecting that each side of the link is in a different VLAN and may well be causing the error you see?

Many thanks

Jonathan

[sanjay.khurana]

Let me try this way into lab.

[Collin Clark]

sanjay.khurana wrote:
Hi ,
I have 2 cisco 6509 Switch at my sites. Both switches are connected thru ethernet connection in routing mode. i am getting NATIVE_VLAN_MISMATCH error 
following is conf of Switch A
!
interface Vlan987
ip address 10.167.13.249 255.255.255.252
interface GigabitEthernet13/2
no ip address
logging event link-status
logging event trunk-status
switchport
switchport access vlan 987
switchport mode access
end
Switch B
interface Vlan911
ip address 10.167.13.250 255.255.255.252
ip summary-address eigrp 100 0.0.0.0 0.0.0.0 5
no ip mroute-cache
end
interface GigabitEthernet2/0/25
switchport access vlan 911
srr-queue bandwidth share 1 70 25 5
srr-queue bandwidth shape  3  0  0  0
priority-queue out
mls qos trust dscp
snmp ifindex persist
arp timeout 300
end
and following is error log
NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on GigabitEthernet13/2 (987), with  GigabitEthernet2/0/25 (911)
as per my knowledge when we have trunk between switches and using switchport trunk native vlan command on both side and vlan id is not same then this type of error is genrate by switch. as of now i don't have trunk between switches then why i am getting this error not understand.
Note : no any other port are member of vlan. 
no any another connection between switches.

There are quite a few things to address here, but lets take each one by one. First, you mention that you want these as routed ports correct? Why don't you have IP's on the interfaces?

[Jeffrey Schroeder]

Just noticed one thing on your configuration for interface GigabitEthernet2/0/25.

You have added "switchport access vlan 911," but did not add "switchport mode access."

If you do not add switchport mode access, the device will still use DTP and attempt to bring the link up as a trunk.

Can you add that to your configuration to see if that resolves the issue?

Thanks,
Jeff

[davy.timmermans]

I 2nd Jeffrey