if input / output drops

Discussion in 'Cisco' started by hack.bac, Apr 27, 2007.

  1. hack.bac

    hack.bac Guest

    Recently, an SNMP monitoring program has been displaying errors for my
    backbone E1. When the link is saturated, downstream traffic gets
    input / output packet drops.

    Is it a smart thing to increase the hold-queue? or disable CEF?

    Platform: Cisco7206VXR

    Serial2/0 is up, line protocol is up
    Hardware is 4ME1-BAL
    Description: E1#1 8:1/2 i8
    Internet address is 10.10.10.34/30
    MTU 1500 bytes, BW 1984 Kbit, DLY 20000 usec,
    reliability 255/255, txload 92/255, rxload 42/255
    Encapsulation HDLC, crc 16, loopback not set
    Keepalive set (10 sec)
    Restart-Delay is 0 secs
    Last input 00:00:00, output 00:00:00, output hang never
    Last clearing of "show interface" counters 2w1d
    Input queue: 0/75/0/15 (size/max/drops/flushes); Total output drops:
    12266
    Queueing strategy: weighted fair
    Output queue: 1/1000/64/12266 (size/max total/threshold/drops)
    Conversations 1/247/256 (active/max active/max total)
    Reserved Conversations 0/0 (allocated/max allocated)
    Available Bandwidth 1488 kilobits/sec
    5 minute input rate 330000 bits/sec, 169 packets/sec
    5 minute output rate 723000 bits/sec, 162 packets/sec
    175347945 packets input, 1677577210 bytes, 0 no buffer
    Received 151254 broadcasts, 0 runts, 0 giants, 0 throttles
    862300 input errors, 861883 CRC, 0 frame, 7 overrun, 0 ignored,
    410 abort
    143679042 packets output, 2524635557 bytes, 0 underruns
    0 output errors, 0 collisions, 2 interface resets
    0 output buffer failures, 0 output buffers swapped out
    2 carrier transitions
    0 alarm indications, 0 remote alarms, 0 rx LOF, 0 rx LOS
    DCD up, BER inactive, NELR inactive, FELR inactive

    Serial2/0 is up, line protocol is up
    Internet address is 10.10.10.34/30
    Broadcast address is 255.255.255.255
    Address determined by non-volatile memory
    MTU is 1500 bytes
    Helper address is not set
    Directed broadcast forwarding is disabled
    Multicast reserved groups joined: 224.0.0.10
    Outgoing access list is not set
    Inbound access list is not set
    Proxy ARP is enabled
    Security level is default
    Split horizon is enabled
    ICMP redirects are always sent
    ICMP unreachables are always sent
    ICMP mask replies are never sent
    IP fast switching is enabled
    IP fast switching on the same interface is enabled
    IP Flow switching is disabled
    IP CEF switching is enabled
    IP Feature Fast switching turbo vector
    IP Feature CEF switching turbo vector
    IP multicast fast switching is enabled
    IP multicast distributed fast switching is disabled
    IP route-cache flags are Fast, CEF
    Router Discovery is disabled
    IP output packet accounting is disabled
    IP access violation accounting is disabled
    TCP/IP header compression is disabled
    RTP/IP header compression is disabled
    Probe proxy name replies are disabled
    Policy routing is disabled
    Network address translation is disabled
    WCCP Redirect outbound is disabled
    WCCP Redirect inbound is disabled
    WCCP Redirect exclude is disabled
    BGP Policy Mapping is disabled
    IP multicast multilayer switching is disabled
    hack.bac, Apr 27, 2007
    #1
    1. Advertising

  2. hack.bac

    Thrill5 Guest

    If the link is saturated, there is nothing you can do to prevent that except
    increase the amount of bandwidth between A and B. The reason you are
    getting output drops is because you are trying to send more traffic than the
    bandwidth you have can send. Input drops are a different story, but the
    number of input drops you have is not an area of concern.

    CEF is a method to populate the hardware routing cache, it has nothing to do
    with input/output drops, except that disabling it will result in more drops
    because it will significantly slow routing performance.

    Scott

    "hack.bac" <> wrote in message
    news:...
    > Recently, an SNMP monitoring program has been displaying errors for my
    > backbone E1. When the link is saturated, downstream traffic gets
    > input / output packet drops.
    >
    > Is it a smart thing to increase the hold-queue? or disable CEF?
    >
    > Platform: Cisco7206VXR
    >
    > Serial2/0 is up, line protocol is up
    > Hardware is 4ME1-BAL
    > Description: E1#1 8:1/2 i8
    > Internet address is 10.10.10.34/30
    > MTU 1500 bytes, BW 1984 Kbit, DLY 20000 usec,
    > reliability 255/255, txload 92/255, rxload 42/255
    > Encapsulation HDLC, crc 16, loopback not set
    > Keepalive set (10 sec)
    > Restart-Delay is 0 secs
    > Last input 00:00:00, output 00:00:00, output hang never
    > Last clearing of "show interface" counters 2w1d
    > Input queue: 0/75/0/15 (size/max/drops/flushes); Total output drops:
    > 12266
    > Queueing strategy: weighted fair
    > Output queue: 1/1000/64/12266 (size/max total/threshold/drops)
    > Conversations 1/247/256 (active/max active/max total)
    > Reserved Conversations 0/0 (allocated/max allocated)
    > Available Bandwidth 1488 kilobits/sec
    > 5 minute input rate 330000 bits/sec, 169 packets/sec
    > 5 minute output rate 723000 bits/sec, 162 packets/sec
    > 175347945 packets input, 1677577210 bytes, 0 no buffer
    > Received 151254 broadcasts, 0 runts, 0 giants, 0 throttles
    > 862300 input errors, 861883 CRC, 0 frame, 7 overrun, 0 ignored,
    > 410 abort
    > 143679042 packets output, 2524635557 bytes, 0 underruns
    > 0 output errors, 0 collisions, 2 interface resets
    > 0 output buffer failures, 0 output buffers swapped out
    > 2 carrier transitions
    > 0 alarm indications, 0 remote alarms, 0 rx LOF, 0 rx LOS
    > DCD up, BER inactive, NELR inactive, FELR inactive
    >
    > Serial2/0 is up, line protocol is up
    > Internet address is 10.10.10.34/30
    > Broadcast address is 255.255.255.255
    > Address determined by non-volatile memory
    > MTU is 1500 bytes
    > Helper address is not set
    > Directed broadcast forwarding is disabled
    > Multicast reserved groups joined: 224.0.0.10
    > Outgoing access list is not set
    > Inbound access list is not set
    > Proxy ARP is enabled
    > Security level is default
    > Split horizon is enabled
    > ICMP redirects are always sent
    > ICMP unreachables are always sent
    > ICMP mask replies are never sent
    > IP fast switching is enabled
    > IP fast switching on the same interface is enabled
    > IP Flow switching is disabled
    > IP CEF switching is enabled
    > IP Feature Fast switching turbo vector
    > IP Feature CEF switching turbo vector
    > IP multicast fast switching is enabled
    > IP multicast distributed fast switching is disabled
    > IP route-cache flags are Fast, CEF
    > Router Discovery is disabled
    > IP output packet accounting is disabled
    > IP access violation accounting is disabled
    > TCP/IP header compression is disabled
    > RTP/IP header compression is disabled
    > Probe proxy name replies are disabled
    > Policy routing is disabled
    > Network address translation is disabled
    > WCCP Redirect outbound is disabled
    > WCCP Redirect inbound is disabled
    > WCCP Redirect exclude is disabled
    > BGP Policy Mapping is disabled
    > IP multicast multilayer switching is disabled
    >
    Thrill5, Apr 27, 2007
    #2
    1. Advertising

  3. hack.bac

    Guest

    On Apr 26, 7:47 pm, "hack.bac" <> wrote:
    > Recently, an SNMP monitoring program has been displaying errors for my
    > backbone E1. When the link is saturated, downstream traffic gets
    > input / output packet drops.
    >
    > Is it a smart thing to increase the hold-queue? or disable CEF?
    >
    > Platform: Cisco7206VXR
    >
    > Serial2/0 is up, line protocol is up
    > Hardware is 4ME1-BAL
    > Description: E1#1 8:1/2 i8
    > Internet address is 10.10.10.34/30
    > MTU 1500 bytes, BW 1984 Kbit, DLY 20000 usec,
    > reliability 255/255, txload 92/255, rxload 42/255
    > Encapsulation HDLC, crc 16, loopback not set
    > Keepalive set (10 sec)
    > Restart-Delay is 0 secs
    > Last input 00:00:00, output 00:00:00, output hang never
    > Last clearing of "show interface" counters 2w1d
    > Input queue: 0/75/0/15 (size/max/drops/flushes); Total output drops:
    > 12266
    > Queueing strategy: weighted fair
    > Output queue: 1/1000/64/12266 (size/max total/threshold/drops)
    > Conversations 1/247/256 (active/max active/max total)
    > Reserved Conversations 0/0 (allocated/max allocated)
    > Available Bandwidth 1488 kilobits/sec
    > 5 minute input rate 330000 bits/sec, 169 packets/sec
    > 5 minute output rate 723000 bits/sec, 162 packets/sec
    > 175347945 packets input, 1677577210 bytes, 0 no buffer
    > Received 151254 broadcasts, 0 runts, 0 giants, 0 throttles
    > 862300 input errors, 861883 CRC, 0 frame, 7 overrun, 0 ignored,
    > 410 abort
    > 143679042 packets output, 2524635557 bytes, 0 underruns
    > 0 output errors, 0 collisions, 2 interface resets
    > 0 output buffer failures, 0 output buffers swapped out
    > 2 carrier transitions
    > 0 alarm indications, 0 remote alarms, 0 rx LOF, 0 rx LOS
    > DCD up, BER inactive, NELR inactive, FELR inactive
    >
    > Serial2/0 is up, line protocol is up
    > Internet address is 10.10.10.34/30
    > Broadcast address is 255.255.255.255
    > Address determined by non-volatile memory
    > MTU is 1500 bytes
    > Helper address is not set
    > Directed broadcast forwarding is disabled
    > Multicast reserved groups joined: 224.0.0.10
    > Outgoing access list is not set
    > Inbound access list is not set
    > Proxy ARP is enabled
    > Security level is default
    > Split horizon is enabled
    > ICMP redirects are always sent
    > ICMP unreachables are always sent
    > ICMP mask replies are never sent
    > IP fast switching is enabled
    > IP fast switching on the same interface is enabled
    > IP Flow switching is disabled
    > IP CEF switching is enabled
    > IP Feature Fast switching turbo vector
    > IP Feature CEF switching turbo vector
    > IP multicast fast switching is enabled
    > IP multicast distributed fast switching is disabled
    > IP route-cache flags are Fast, CEF
    > Router Discovery is disabled
    > IP output packet accounting is disabled
    > IP access violation accounting is disabled
    > TCP/IP header compression is disabled
    > RTP/IP header compression is disabled
    > Probe proxy name replies are disabled
    > Policy routing is disabled
    > Network address translation is disabled
    > WCCP Redirect outbound is disabled
    > WCCP Redirect inbound is disabled
    > WCCP Redirect exclude is disabled
    > BGP Policy Mapping is disabled
    > IP multicast multilayer switching is disabled


    Try to disable WFQ - use FIFO on high speed interfaces. increasing
    hold queue should be your last resort.
    , Apr 27, 2007
    #3
  4. hack.bac

    Guest

    On 27 Apr, 02:55, wrote:
    > On Apr 26, 7:47 pm, "hack.bac" <> wrote:
    >
    >
    >
    >
    >
    > > Recently, an SNMP monitoring program has been displaying errors for my
    > > backbone E1. When the link is saturated, downstream traffic gets
    > > input / output packet drops.

    >
    > > Is it a smart thing to increase the hold-queue? or disable CEF?

    >
    > > Platform: Cisco7206VXR

    >
    > > Serial2/0 is up, line protocol is up
    > > Hardware is 4ME1-BAL
    > > Description: E1#1 8:1/2 i8
    > > Internet address is 10.10.10.34/30
    > > MTU 1500 bytes, BW 1984 Kbit, DLY 20000 usec,
    > > reliability 255/255, txload 92/255, rxload 42/255
    > > Encapsulation HDLC, crc 16, loopback not set
    > > Keepalive set (10 sec)
    > > Restart-Delay is 0 secs
    > > Last input 00:00:00, output 00:00:00, output hang never
    > > Last clearing of "show interface" counters 2w1d
    > > Input queue: 0/75/0/15 (size/max/drops/flushes); Total output drops:
    > > 12266
    > > Queueing strategy: weighted fair
    > > Output queue: 1/1000/64/12266 (size/max total/threshold/drops)
    > > Conversations 1/247/256 (active/max active/max total)
    > > Reserved Conversations 0/0 (allocated/max allocated)
    > > Available Bandwidth 1488 kilobits/sec
    > > 5 minute input rate 330000 bits/sec, 169 packets/sec
    > > 5 minute output rate 723000 bits/sec, 162 packets/sec
    > > 175347945 packets input, 1677577210 bytes, 0 no buffer
    > > Received 151254 broadcasts, 0 runts, 0 giants, 0 throttles
    > > 862300 input errors, 861883 CRC, 0 frame, 7 overrun, 0 ignored,
    > > 410 abort
    > > 143679042 packets output, 2524635557 bytes, 0 underruns
    > > 0 output errors, 0 collisions, 2 interface resets
    > > 0 output buffer failures, 0 output buffers swapped out
    > > 2 carrier transitions
    > > 0 alarm indications, 0 remote alarms, 0 rx LOF, 0 rx LOS
    > > DCD up, BER inactive, NELR inactive, FELR inactive

    >
    > > Serial2/0 is up, line protocol is up
    > > Internet address is 10.10.10.34/30
    > > Broadcast address is 255.255.255.255
    > > Address determined by non-volatile memory
    > > MTU is 1500 bytes
    > > Helper address is not set
    > > Directed broadcast forwarding is disabled
    > > Multicast reserved groups joined: 224.0.0.10
    > > Outgoing access list is not set
    > > Inbound access list is not set
    > > Proxy ARP is enabled
    > > Security level is default
    > > Split horizon is enabled
    > > ICMP redirects are always sent
    > > ICMP unreachables are always sent
    > > ICMP mask replies are never sent
    > > IP fast switching is enabled
    > > IP fast switching on the same interface is enabled
    > > IP Flow switching is disabled
    > > IP CEF switching is enabled
    > > IP Feature Fast switching turbo vector
    > > IP Feature CEF switching turbo vector
    > > IP multicast fast switching is enabled
    > > IP multicast distributed fast switching is disabled
    > > IP route-cache flags are Fast, CEF
    > > Router Discovery is disabled
    > > IP output packet accounting is disabled
    > > IP access violation accounting is disabled
    > > TCP/IP header compression is disabled
    > > RTP/IP header compression is disabled
    > > Probe proxy name replies are disabled
    > > Policy routing is disabled
    > > Network address translation is disabled
    > > WCCP Redirect outbound is disabled
    > > WCCP Redirect inbound is disabled
    > > WCCP Redirect exclude is disabled
    > > BGP Policy Mapping is disabled
    > > IP multicast multilayer switching is disabled

    >
    > Try to disable WFQ - use FIFO on high speed interfaces. increasing
    > hold queue should be your last resort.- Hide quoted text -
    >
    > - Show quoted text -


    A couple of things here:

    More concerning than the drops are the CRC errors.
    Maybe though they are historic?

    Also, in general increasing buffer sizes is a bad thing.
    I know it sounds like a good thing but it is usually not
    and will never I don't think be a good thing of the line
    is saturated.

    In the saturated case what you get by adding more
    output buffer is that you change from

    - A saturated line

    to

    - A saturated line with more delay.

    I am now very much against large buffers.

    Here is an little analogy.

    Imagine that the local supermarkets were required by
    law to do queuing in the same way as routers do it.
    The queue is hidden from the customer in a big lightless
    box such that customers (packets) cannot at any instant
    determine the size of the queue. Also if the queue is full
    customers are turned away by security at the queue
    entrance and ejected from the supermarket.

    If the supermarket is busy enough you will be able to find
    information on the instantaneous and maximum queue size
    by measuring the time spent queueing at each visit.

    I don;t know about you but I would be tempted to find out
    the relative 'hidden' queue sizes and go to the one with
    the smallest hidden queue.

    If then the stores were required to announce the
    Maximum queue size (number of output packet buffers)
    I woudl be drawn to the one with the smaller number.

    Good luck.
    , Apr 27, 2007
    #4
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