Native Vlan Mismatch error

[Someone]

I got two errors showing up on console:

(1) 4w5d: %LINK-4-ERROR: FastEthernet0/3 is experiencing errors

(2) 4w5d: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered
on FastEthernet0/16 (20), with Switch3 FastEthernet0/48 (1).
Also, one port on one of the switch is flapping.

There are there switches on this rack connected by both fiber and
crossover cable. How can I fix these problems. Thanks.

[Trendkill]

Change the native vlan on both switches to match. If its IOS based, I
would think you need to do a switchport mode access, switchport access
vlan <nativevlan>. Then put your trunk statements back. On the
catalyst side, set vlan <port> <nativevlan>, and then you again may
need you put your trunking statements back. Its probably not a major
issue, but you want your trunks in the same native vlan before
configuring trunking.

[notaccie]

if you are just passing traffic across a common vlan,no trunking, set
each port to the same vlan and access mode.

If you are using 802.1q, though, you might want to define a native
vlan for each dot1q trunk. The native vlan won't be tagged, and allow
only the desired vlans to pass through. Don't use the native vlan
number anywhere else in your net.

if 888 is the native vlan and you want to pass 5,6,7 then something
like this works. add other i/f commands as suits your env.

IOS:

interface command:

switchport
switchport trunk encapsulation dot1q
switchport trunk native vlan 888
switchport trunk allowed vlan 5-7
switchport mode trunk
etc.

catos:

set vlan 888 mod/port

set trunk mod/port <desireable, on, ...> dot1q 5-7

works well. the next dot1q tunnel you define might use 889 for the
native vlan, etc. keep track, as always, of where vlans occur. keep
as local as possible.