Unknown protocol drops

[fred.gardner]

I'm receiving the following display on a 2811 fast ethernet connection and am not sure what it means:

FastEthernet0/0 is up, line protocol is up

20 unknown protocol drops

[fred.gardner]

I car pool, so I can't tonight, but I will tomorrow. Thanks for your input...!

Fred

[fred.gardner]

Here's the router Fa0/0:

interface FastEthernet0/0

description LAN interface at 700 E Santa Fe St Olathe

ip address 192.168.231.1 255.255.255.0 secondary

ip address 10.10.46.1 255.255.255.0 secondary

ip address 10.110.81.1 255.255.255.0

ip helper-address 192.168.48.50

ip helper-address 172.17.48.50

no ip redirects

no ip unreachables

ip directed-broadcast 143

no ip proxy-arp

no ip mroute-cache

duplex full

speed 100

no mop enabled

and the switch:

interface FastEthernet0/1

description Connection to Branch Router

duplex full

speed 100

[mark.cronin]

on the switch can you issue this command

show int fa 0/1 switchport

[Yudong Wu]

By default, "Negotiation of Trunking" is in "ON" status. Please check the switch port to "access mode". "switch mode access".

[mark.cronin]

I have not got a 2924 to test with but

I think it uses DISL rather than DTP

[Yudong Wu]

Yes, you could be right.

I would like to turn off any trunk negociation.

[fred.gardner]

UMB208SW11#show int fa 0/1 switchport

Name: Fa0/1

Switchport: Enabled

Administrative mode: static access

Operational Mode: static access

Administrative Trunking Encapsulation: isl

Operational Trunking Encapsulation: isl

Negotiation of Trunking: Disabled

Access Mode VLAN: 1 (default)

Trunking Native Mode VLAN: 1 (default)

Trunking VLANs Enabled: NONE

Pruning VLANs Enabled: NONE

Priority for untagged frames: 0

Override vlan tag priority: FALSE

Voice VLAN: none

Appliance trust: none

Self Loopback: No

[mark.cronin]

"Negotiation of Trunking: Disabled"

Well thats put a stop to that idea.

Can you put the switchport in to portfast mode.

I think you are going to need to install wireshark on a laptop and SPAN that port to look for the unknown protocol or during out of hours over a weekend look at using debug commands (ip packet detail - be carefull" on the router.

Have you got a hosts / printers on that switch with protocols like IPX DLC/LLC running?

[Yudong Wu]

Agree. we have to do a sniffer to find out what the packet causes the drop if you don't know what else traffic is on that link.