Input error on trunk interface.

Unanswered Question
Apr 8th, 2009

I've seen approximately 90.000 input errors on a gigabit ethernet trunk port of a 4510 chassis. Configuration is as follows;


interface GigabitEthernet3/1

switchport trunk encapsulation dot1q

switchport trunk native vlan 3

switchport mode trunk


The other end of the loop was on a 3750, with a configuration like;


interface GigabitEthernet1/0/24

switchport trunk encapsulation dot1q

switchport trunk native vlan 3


After configuring dynamic desirable interface to mode trunk, input errors stopped increasing.

What can be a logical explanation to this situation guys, we are not getting crc's, only input errors, is this normal?

Thanx in advance.


I have this problem too.
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Giuseppe Larosa Wed, 04/08/2009 - 12:35

Hello Baha,

if the side with dynamic desirable puts itself in access mode all frames with a vlan tag different then the access vlan should be discarded.

the behaviour can be dynamic and depends from the fact that the other side can be willing to negotiate or not.

Another possibility is that DTP exchanges information about VTP domain if VTP domain changes a dynamic desirable port will not become trunk.

Hope to help


baha.dericiogullari Wed, 04/08/2009 - 12:49

BTW here below are the average RX/TX rates on the indicated days.

GigabitEthernet3/1 - Gi3/1

Avrg RX Avrg TX

07-Apr-09 12 Mbps 78 Mbps

06-Apr-09 4,42 Mbps 78 Mbps

08-Apr-09 5,08 Mbps 81 Mbps


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