关于NATIVE_VLAN_MISMATCH 的排错分析

核心交换机划分access模式的VLAN，二级交换机级联口设置为default模式，连接后两台交换机都提示：
00:07:05: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on FastEthernet0/3 (3), with Switch GigabitEthernet0/1 (1).

  

解决步骤：
观察核心交换机，端口设置如下
SW1#sh run int f0/3
interface FastEthernet0/3

switchport access vlan 3

switchport mode access

SW1#sh int f0/3 swi
Name: Fa0/3
Switchport: Enabled
Administrative Mode: static access
Operational Mode: static access
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: native
Negotiation of Trunking: Off
Access Mode VLAN: 3 (VLAN0003)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk private VLANs: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
         
Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Appliance trust: none
----------------------------------------------------------

二级交换机上连端口如下：
Switch#sh run int 0/1
interface GigabitEthernet0/1
end
Switch#sh int g0/1 swi
Name: Gi0/1
Switchport: Enabled
Administrative Mode: dynamic auto
Operational Mode: static access
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: native
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk private VLANs: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
         
Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Appliance trust: none

 

 

主要是核心交换机上:

Access模式下的Native为Access Mode VLAN: 3 (VLAN0003)
而Trunk模式下的Native为Trunking Native Mode VLAN: 1 (default)

原因：
经过查阅cisco相关资料，Cisco在IOS 12.0(3)以後，已经改用CDP version 2了，增加了VTP Management Domain Name、Native VLAN，以及full/half-Duplex三个特征位，链路两端的Access Mode VLAN不一致，因此交换机日志会提示”%CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on FastEthernet0/3 (3), with Switch GigabitEthernet0/1 (1)”

解决办法：
解决办法就是不启用VTP version2，在全局配置模式下输入命令
Switch(config)#no cdp advertise-v2
强制交换机使用version1，通过命令再查看CDP的信息可以看到已经使用version 1进行通讯。
Switch#sh cdp traffic
CDP counters :

Total packets output: 26, Input: 50

Hdr syntax: 0, Chksum error: 0, Encaps failed: 0

No memory: 0, Invalid packet: 0, Fragmented: 0

CDP version 1 advertisements output: 26, Input: 25


CDP version 2 advertisements output: 0, Input: 25