input queue drops

[Kashish_Patel]

I am seeing large no. of input queue drops

wan2.dr.shaw.net#sh int fa4/0/1   

FastEthernet4/0/1 is up, line protocol is up

  Hardware is i82543 FastEthernet Interface, address is 001c.b0b7.9a00 (bia 001c.b0b7.9a00)

  Description: <>

  Internet address is 10.236.2.153/30

  MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec,

     reliability 255/255, txload 1/255, rxload 1/255

  Encapsulation ARPA, loopback not set

  Keepalive set (10 sec)

  Full-duplex, 10Mb/s, 100BaseTX/FX

  ARP type: ARPA, ARP Timeout 04:00:00

  Last input 00:00:00, output 00:00:01, output hang never

  Last clearing of "show interface" counters 01:05:42

  Input queue: 0/75/64771/0 (size/max/drops/flushes); Total output drops: 0

  Queueing strategy: Class-based queueing

  Output queue: 0/40 (size/max)

  30 second input rate 29000 bits/sec, 17 packets/sec

  30 second output rate 29000 bits/sec, 17 packets/sec

     68491 packets input, 14287966 bytes, 0 no buffer

     Received 1224 broadcasts (0 IP multicasts)

     0 runts, 0 giants, 0 throttles

     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

     0 watchdog

     0 input packets with dribble condition detected

     67760 packets output, 14272427 bytes, 0 underruns

     0 output errors, 0 collisions, 0 interface resets

     0 babbles, 0 late collision, 0 deferred

     0 lost carrier, 0 no carrier

     0 output buffer failures, 0 output buffers swapped out

I have gone through

http://www.cisco.com/en/US/products/hw/routers/ps133/products_tech_note09186a0080094791.shtml

and I found that bad hop count in the output of "show ip traffic" is increasing very rapidly.

wan2.dr.shaw.net#sh ip traffic

IP statistics:

  Rcvd:  2921587179 total, 1080849054 local destination

         0 format errors, 0 checksum errors, 1618080527 bad hop count

         0 unknown protocol, 221531 not a gateway

         0 security failures, 0 bad options, 1199608 with options

Can this be the problem? If yes, how to rectify it?

Platform is

CISCO7604 and IOS running is

c7600rsp72043-advipservicesk9-mz.122-33.SRB1.bin

Thanks,

Kashish

[shaijo.mohan]

I had seen this problem once and was caused by a bad router in the same Ethernet segment.  The troubled router was forwarding floods of packets and was causing input drops and high CPU

In the given ‘IP traffic’ output, there are lot of 'not a gateway' error as well. You can please check for any possible routing inconsistency in the network and routing loops

[Raju Sekharan]

Hi Kashish

Input queue drops can happen if

1. if you have an input service-policy policing the packets

2. There is high number of process switched packets from that interface

bad-hop count increase the 2nd reason

to isolate the issue

1. 1st check if there in any input-service policy

2. If there is none, use a netdr to capture the packets hitting the CPU from that interface

Steps for netdr capture

a) debug netdr capture rx interface fa4/0/1

b) wait got 1 or 2 minutes

c) show netdr captured-packets

Thanks

Raju

Thanks

Raju

[Kashish_Patel]

Thanks rajs2..

We have service policy in output direction but none in input direction...

will netdr capture affect router functioning? this is our production router.

Also I am seeing drops increasing in "sh int switching" output

wan2.dr.shaw.net#sh int fa4/0/1 switching | i Drops

        Drops         RP     265090         SP          0

SPD Priority     Inputs          0      Drops          0

looks like RP is causing drops

[Raju Sekharan]

Hi Kashish

Netdr you an run any production router. It doesn't cause any impact

Thanks

Raju

[rikdrt1]

can you use netdr on a VL interface also ?  i have similar issue with 1 of 2 voice vlans having a large number of drops. 

never used that command, but will look into it for sure. 

thanks.