unknown protocol drops on interfaces

[CSCO11460466]

Hello everyone

I have a Cisco router C1700 and it is presenting unknow errors on Serial 0/0 and fa0/0 interfaces.

Does anybody have an idea why this counter is increasing?? Im not very sure if is by CDP neighbors or Vlans that are not configured on a switch attached.

I undertand that the unknown protocol drops field displayed in the above example refers to the  total number of packets dropped due to unknown or unsupported types of protocol.

But anyone have any other suggestion in oder to solve this unknow DROPS?

Thanks in addition

Interface                  IP-Address      OK? Method Status                Protocol

FastEthernet0/0            unassigned      YES NVRAM  up                    up     

FastEthernet0/0.1          129.109.1.254   YES NVRAM  up                    up     

FastEthernet0/0.2          172.24.0.230    YES NVRAM  up                    up     

FastEthernet0/0.5          172.16.147.142  YES NVRAM  up                    up     

FastEthernet0/0.7          172.16.147.150  YES NVRAM  up                    up     

Serial0/0                  201.129.39.202  YES NVRAM  up                    up     










Serial0/0 is up, line protocol is up

  Hardware is PowerQUICC Serial

  Description: ENLACE A UNINET_RPV FOLIO A32-0812-0111

  Internet address is 201.129.39.202/30

  Backup interface Dialer10, failure delay 20 sec, secondary disable delay 60 sec,

  kickin load not set, kickout load not set

  MTU 1500 bytes, BW 1948 Kbit, DLY 20000 usec,

     reliability 255/255, txload 2/255, rxload 6/255

  Encapsulation PPP, LCP Open

  Open: IPCP, CDPCP, loopback not set

  Keepalive set (10 sec)

  Last input 00:00:00, output 00:00:00, output hang never

  Last clearing of "show interface" counters 1d01h

  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 3

  Queueing strategy: weighted fair

  Output queue: 0/1000/64/0 (size/max total/threshold/drops)

     Conversations  0/14/256 (active/max active/max total)

     Reserved Conversations 0/0 (allocated/max allocated)

     Available Bandwidth 1461 kilobits/sec

  5 minute input rate 46000 bits/sec, 6 packets/sec

  5 minute output rate 21000 bits/sec, 7 packets/sec

     855889 packets input, 348526935 bytes, 0 no buffer

     Received 0 broadcasts, 0 runts, 0 giants, 0 throttles

     184 input errors, 145 CRC, 7 frame, 0 overrun, 0 ignored, 32 abort

     855320 packets output, 188034850 bytes, 0 underruns

     0 output errors, 0 collisions, 0 interface resets

     1646 unknown protocol drops------------------------------------------------------------------------>>>>> WHY???

     0 output buffer failures, 0 output buffers swapped out

     0 carrier transitions

     DCD=up  DSR=up  DTR=up  RTS=up  CTS=up

[Latchum Naidu]

Unknown protocol drops reports the packets with unknown or un-configured protocol on a per interface basis. Therefore it can be any protocol that the router doesn’t recognize.

And it is possible you're receiving protocols you don't have configured - IPX, Appletalk, IPv6, some other.

I would suggest you to put a sniffer on the line, it will show you everything passing through the nic.  Wiresharp or ethereal are the best sniffers so that you can know what causing to this unknown procotol drops.

Hope this helps you.

Please rate the helpfull posts.
Regards,
Naidu.

[CSCO11460466]

Hello

Thanks for your help

Im gonna sniff the device in order to check with protocols are been passing.

Regards

[gfcisco31]

hi...

i had this problem once.

And the problem was that, the router had CDP enables and it was connected to another switch that wasn´t configured with CDP..  After i enabled CDP the drop count stopped.

hope that helps

[xthuijs · Accepted solution]

hey guys,

Looks like my article I just wrote is right on time.

It is focussed on the ASR9000, but it gives you a good idea on whatis going on with these protocol drops which seems alarming, but it is not that bad

check this reference and let me know if there are any open items after reading that...

Unrecognized Protocol Drops

regards!

xander

[FlorianCokl]

Hey - the link is a 404?

[rafafilho11]

Where is the currently link ? the old one was disabled

https://community.cisco.com/docs/DOC-15490

[BrianSekleckiGE]

This link is dead as well: Page not found

[JamesEwing]

The link no longer works.  Can you please repost? 

[rameshranga]

Hi i have two routers production A and B , A is ASR 920 and B is Cisco IOS Software, ME380x devices  running L2 link  and we have service instance configured both end. but A router getting continues unknown protocol drops

[FlorianCokl]

Hey CSCO11460466

It is indeed what several users have reported here. I myself have seen it many times - and was wondering wth was going on. I can report from personal experience that for instance a switchport had this counter increasing - hm - the "solution" was so simple = the connected host had LLDP running, and the switchport didn't.  I had configured then LLDP, reset interface counters, and what a surprise, the counter stayed at "0". Once I had LLDP disabled again, the counter for unknown protocol drops was rising again.

So what is the conclusion? I would say nothing? What should I be worried about, honestly? The host was sending LLDP-Frames, LLDP not enabled on the port where this host was attached to - nothing wrong there. Unknown protocol drops "just" means that the connected host is sending frames that the port doesn't know of, or is not configured for?

[mohd abdul malik]

Hi Guys,

I am also seeing the same error on my 9200 switches. i would like to know if sniffing is the only way that can give us the dropped protocol errors? If there is any other way do let me know.

Thanks.

[victoriamyatt]

we are also seeing this on trunk ports connected to C7000 Chassis