I am getting CDP NATIVE VLAN MISMATCH logs on my Cisco 3750x switch stack.
Gig 2/0/5 and Gig 4/0/6 are in no way physically connected to each other (neither is 1/0/44 and 2/0/13 as you'll see below). I interconnect each switch via Stackwise cabling. I haven't seen any performance issues regarding this. Possibly a bug? I'm running 15.2(4)E9 on all of the following switches
Dec 6 17:06:11: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on GigabitEthernet2/0/5 (10), with 3750X_STACK GigabitEthernet4/0/6 (50).
Dec 6 17:06:11: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on GigabitEthernet2/0/5 (10), with 3750X_STACK GigabitEthernet4/0/6 (50). (3750X_STACK-2)
Dec 6 17:07:07: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on GigabitEthernet4/0/6 (50), with 3750X_STACK GigabitEthernet2/0/5 (10).
Dec 6 17:07:07: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on GigabitEthernet4/0/6 (50), with 3750X_STACK GigabitEthernet2/0/5 (10). (3750X_STACK-4)
Dec 6 17:07:10: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on GigabitEthernet2/0/5 (10), with 3750X_STACK GigabitEthernet4/0/6 (50).
Dec 6 17:07:10: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on GigabitEthernet2/0/5 (10), with 3750X_STACK GigabitEthernet4/0/6 (50). (3750X_STACK-2)
Dec 6 17:07:59: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on GigabitEthernet2/0/5 (10), with 3750X_STACK GigabitEthernet4/0/6 (50).
Dec 6 17:07:59: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on GigabitEthernet2/0/5 (10), with 3750X_STACK GigabitEthernet4/0/6 (50). (3750X_STACK-2)
Dec 6 17:08:07: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on GigabitEthernet4/0/6 (50), with 3750X_STACK GigabitEthernet2/0/5 (10).
Dec 6 17:08:07: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on GigabitEthernet4/0/6 (50), with 3750X_STACK GigabitEthernet2/0/5 (10). (3750X_STACK-4)
3750X_STACK#show switch detail
Switch/Stack Mac Address : xxxx.xxxx.xxxx
H/W Current
Switch# Role Mac Address Priority Version State
----------------------------------------------------------
*1 Master xxxx.xxxx.xxxx 15 3 Ready
2 Member xxxx.xxxx.xxxx 1 3 Ready
3 Member xxxx.xxxx.xxxx 1 3 Ready
4 Member xxxx.xxxx.xxxx 1 3 Ready
Stack Port Status Neighbors
Switch# Port 1 Port 2 Port 1 Port 2
--------------------------------------------------------
1 Ok Ok 2 4
2 Ok Ok 3 1
3 Ok Ok 4 2
4 Ok Ok 1 3
3750X_STACK#show cdp neighbors
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone,
D - Remote, C - CVTA, M - Two-port Mac Relay
Device ID Local Intrfce Holdtme Capability Platform Port ID
3750X_STACK
Gig 2/0/5 171 R S I WS-C3750X Gig 4/0/6
3750X_STACK
Gig 4/0/6 131 R S I WS-C3750X Gig 2/0/5
3750X_STACK
Gig 2/0/13 150 R S I WS-C3750X Gig 1/0/44
3750X_STACK
Gig 1/0/44 147 R S I WS-C3750X Gig 2/0/13
Switch Ports Model SW Version SW Image
------ ----- ----- ---------- ----------
* 1 54 WS-C3750X-48P 15.2(4)E9 C3750E-UNIVERSALK9-M
2 54 WS-C3750X-48P 15.2(4)E9 C3750E-UNIVERSALK9-M
3 54 WS-C3750X-48P 15.2(4)E9 C3750E-UNIVERSALK9-M
4 54 WS-C3750X-48P 15.2(4)E9 C3750E-UNIVERSALK9-M
3750X_STACK#show run interface gigabitEthernet 2/0/5
Building configuration...
Current configuration : 151 bytes
!
interface GigabitEthernet2/0/5
switchport access vlan 10
switchport trunk encapsulation dot1q
switchport mode access
end
3750X_STACK#show run interface gigabitEthernet 4/0/6
Building configuration...
Current configuration : 106 bytes
!
interface GigabitEthernet4/0/6
switchport access vlan 50
switchport mode access
end
Best Answer
This happens when something downstream of the switch doesn't understand CDP and mishandles the traffic. So, something is connecting 2/0/5 to 4/0/6; chase the wiring and you'll find it. (someone has a dumb switch, or dumb VM leaking traffic)