From: boby2kusa@hotmail.com
Date: Mon Aug 25 2003 - 16:05:22 GMT-3
jonathan,
The error seems to be on fa0/20 on both the switches NOT fa0/19:
00:19:24: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered
> on FastEthernet0/20 (2), with S1_3550 FastEthernet0/20 (1).
These devices have trunking on desirable by default check the S1_3550 if
it's trunking.
----- Original Message -----
From: "Jonathan V Hays" <jhays@jtan.com>
To: <ccielab@groupstudy.com>
Sent: Monday, August 25, 2003 11:44 AM
Subject: FW: Cat3550: ISL native VLAN mismatch?
> All,
>
> While playing around with Emad's config (see "Cat3550: strange problem")
> I came across an unexpected error message:
>
> "00:19:24: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered
> on FastEthernet0/20 (2), with S1_3550 FastEthernet0/20 (1)."
>
> Physically, ports fa0/19 and fa0/20 are connected between two Catalyst
> 3550 switches with crossover cables. I configured fa0/19 as an ISL
> trunk. I then configured fa0/20 on switch 2 (S2_3550) with VLAN 2 and
> got the error.
>
> I thought 'native vlan' applied only to Dot1Q trunks. Evidently not. I
> guess I need to reread the switch software configuration guide.
>
> A minute later I remembered that configuring a port with vlan 2 was not
> necessary for what I was trying to accomplish so I removed it from
> fa0/20. All I needed to do was to create the VLAN. The command
> "interface vlan 2" does not create a VLAN, although "switchport access
> vlan 2" does create a VLAN. And of course you can simply create the vlan
> without applying it to an interface, using either "config-vlan Mode" or
> "VLAN Configuration Mode", as Cisco calls them. I think Cisco could have
> created more distinctive terms for these two modes.
>
> Here's the link for those unfamiliar with these two modes:
>
> http://www.cisco.com/univercd/cc/td/doc/product/lan/c3550/12114ea1/3550s
> cg/swvlan.htm#1196935
>
> Does anyone have an insight into the cause of this error message?
>
>
> No VLANs had been created at this point and the configs were as follows:
>
> SWITCH 1:
> =========
> interface FastEthernet0/19
> switchport trunk encapsulation isl
> switchport mode trunk
> no ip address
> !
> interface Vlan2
> ip address 20.1.1.1 255.255.255.0
> !
> interface Vlan3
> ip address 30.1.1.1 255.255.255.0
> !
> ip default-gateway 20.1.1.2
> ip classless
>
> SWITCH 2:
> =========
> interface FastEthernet0/19
> switchport trunk encapsulation isl
> switchport mode trunk
> no ip address
> !
> interface FastEthernet0/20
> switchport access vlan 2
> switchport mode access
> no ip address
> !
> interface Vlan2
> ip address 20.1.1.2 255.255.255.0
> =========
> AFTER CONFIGURING FA0/20:
> =========
> S2_3550(config)#in fa0/20
> S2_3550(config-if)#switchport mode access
> S2_3550(config-if)#switchport access vlan 2
> % Access VLAN does not exist. Creating vlan 2
> S2_3550(config-if)#
> 00:19:24: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered
> on FastEthernet0/20 (2), with S1_3550 FastEthernet0/20 (1).
> S2_3550(config-if)#
> 00:19:48: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan2, changed
> state to up
> S2_3550(config-if)#
> 00:20:24: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered
> on FastEthernet0/20 (2), with S1_3550 FastEthernet0/20 (1).
> S2_3550(config-if)#
>
> The same error message appeared on the other switch.
>
> Thanks for your comments,
>
> Jonathan
>
>
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