[c-nsp] Unexplainable Output drops on serial interfaces

[David Freedman]

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What about the VIP CPU load on these VIPs? do you graph it?

Todd Shipway wrote:
> The multilink interface had qos setup but not on the individual serial
> interfaces.  However I am seeing these drops on interfaces with no qos
> or shaping on them as well.
> 
> 
> On Feb 19, 2009, at 3:03 PM, "David Freedman"
> <david.freedman at uk.clara.net> wrote:
> 
>> Todd, do you have any kind of shaping / QoS on these circuits?
>>
>> Drops by traffic management configurations are frequently shown as
>> interface drops.
>>
>> Dave.
>>
>>
>> Todd Shipway wrote:
>>> Hi,
>>>
>>> We have multiple T1 interfaces across different cards and different type
>>> of cards in a 7513.  Many interfaces are showing output drops and I
>>> can't pinpoint why.  The interfaces are spread throughout the system and
>>> I can't pinpoint a single point that could be causing the drops.  Below
>>> is 2 interfaces showing the drops.
>>>
>>> The bandwidth is very low when the drops are occurring, these 2
>>> interfaces are part of a multilink interface which shows no drops.  Any
>>> ideas as to what I should look for that could be causing this?
>>>
>>> Serial9/0/0:12 is up, line protocol is up
>>>  Hardware is cyBus T3
>>>  Description: Bonded T1
>>>  MTU 1500 bytes, BW 1540 Kbit, DLY 20000 usec,
>>>     reliability 255/255, txload 11/255, rxload 5/255
>>>  Encapsulation PPP, LCP Open, multilink Open
>>>  Link is a member of Multilink bundle Multilink66, crc 16, 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 6d03h
>>>  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops:
>>> 4050
>>>  Queueing strategy: fifo
>>>  Output queue: 0/100 (size/max)
>>>  5 minute input rate 33000 bits/sec, 19 packets/sec
>>>  5 minute output rate 68000 bits/sec, 18 packets/sec
>>>     3121597 packets input, 667733893 bytes, 0 no buffer
>>>     Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
>>>     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
>>>     2929740 packets output, 1363133541 bytes, 0 underruns
>>>     0 output errors, 0 collisions, 0 interface resets
>>>     0 output buffer failures, 0 output buffers swapped out
>>>     0 carrier transitions no alarm present
>>>  Timeslot(s) Used: 1-24, Transmitter delay is 0 flags
>>>  non-inverted data
>>>
>>> Serial9/0/0:11 is up, line protocol is up
>>>  Hardware is cyBus T3
>>>  Description: Bonded T1
>>>  MTU 1500 bytes, BW 1540 Kbit, DLY 20000 usec,
>>>     reliability 255/255, txload 10/255, rxload 5/255
>>>  Encapsulation PPP, LCP Open, multilink Open
>>>  Link is a member of Multilink bundle Multilink66, crc 16, 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 6d03h
>>>  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops:
>>> 4085
>>>  Queueing strategy: fifo
>>>  Output queue: 0/100 (size/max)
>>>  5 minute input rate 31000 bits/sec, 19 packets/sec
>>>  5 minute output rate 65000 bits/sec, 17 packets/sec
>>>     3122847 packets input, 668516220 bytes, 0 no buffer
>>>     Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
>>>     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
>>>     2930011 packets output, 1364226428 bytes, 0 underruns
>>>     0 output errors, 0 collisions, 0 interface resets
>>>     0 output buffer failures, 0 output buffers swapped out
>>>     0 carrier transitions no alarm present
>>>  Timeslot(s) Used: 1-24, Transmitter delay is 0 flags
>>>  non-inverted data
>>>
>>> Multilink interface for the T1's above:
>>> Multilink66 is up, line protocol is up
>>>  Hardware is multilink group interface
>>>  Description: Bonded T1
>>>  Internet address is 10.10.56.1/30
>>>  MTU 1500 bytes, BW 3080 Kbit, DLY 100000 usec,
>>>     reliability 255/255, txload 11/255, rxload 4/255
>>>  Encapsulation PPP, LCP Open, multilink Open
>>>  Open: IPCP, loopback not set
>>>  Keepalive set (10 sec)
>>>  DTR is pulsed for 2 seconds on reset
>>>  Last input 00:00:30, output never, output hang never
>>>  Last clearing of "show interface" counters 1w0d
>>>  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
>>>  Queueing strategy: Class-based queueing
>>>  Output queue: 0/40 (size/max)
>>>  5 minute input rate 58000 bits/sec, 47 packets/sec
>>>  5 minute output rate 139000 bits/sec, 49 packets/sec
>>>     7075294 packets input, 1705142684 bytes, 0 no buffer
>>>     Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
>>>     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
>>>     7483773 packets output, 3524642362 bytes, 0 underruns
>>>     0 output errors, 0 collisions, 0 interface resets
>>>     0 output buffer failures, 0 output buffers swapped out
>>>     0 carrier transitions
>>>
>>> Any help would be appreciated.  As I said earlier, this scenario is
>>> happening on multiple interfaces throughout the system.  A Channelized
>>> DS3 card has been swapped out as a test as well as the output queue
>>> raised from 40 to 100 with no change in drops.
>>>
>>> -Todd
>>>
>>>
>>>
>>> ------------------------------------------------------------------------
>>>
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>>

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