unknown protcol drop

moamen.elhefnawy · ‎03-16-2009

Hello

do any one know what does that mean in show interface fastether0/0 counter

unknown protcol drop , and why it increases

Thanks & BR

Moamen

Giuseppe Larosa · ‎03-16-2009

Hello Moamen,

this error counter increments when frames that are correct at OSI layer 2 carry inside a protocol type that is not known or not running on the fas0/0 interface.

Example:

IS-IS packets are not ip packets we use it for routing, access layer switches count is-is hellos as unknown because they are not running IS-IS.

There are other possible reasons : ipv6 packets or layer 2 signalling packets like VTP or STP and others

if they increment regurarly over time like 1 one every 10 seconds or some every few seconds the reason is a not understood protocol.

if the number is not great you should be fine (no issues for your router)

Hope to help

Giuseppe

moamen.elhefnawy · ‎03-16-2009

Hello,

Thanks fr your help, just do you have any document on Cisco support that , as our customer need such document becuse he think it is a problem .

Thanks & BR

Moamen

Giuseppe Larosa · ‎03-16-2009

Hello Moamen,

unfortunately I couldn't find a clear explanation.

I tried to look at the command reference

http://www.cisco.com/en/US/docs/ios/interface/command/reference/ir_s4.html#wp1019043

However, if no real issue is seen in the network this is a so called cosmetic problem.

Hope to help

Giuseppe

eborcher · ‎03-16-2009

Hi,

Can you provide us with the following output:

(1) show interface fastethernet 0/0 counter

(2) show interface fastethernet 0/0

(3) show version