Input flushes on the 3845 router port

[Difan Zhao]

Could you tell me what this means? Will this cause any issues? Thanks!

#sh int g0/1

GigabitEthernet0/1 is up, line protocol is up

  Hardware is BCM1125 Internal MAC, address is 001a.6d00.a6e1 (bia 001a.6d00.a6e1)

  Description: xxx

  MTU 1500 bytes, BW 60000 Kbit/sec, DLY 100 usec,

     reliability 255/255, txload 29/255, rxload 13/255

  Encapsulation 802.1Q Virtual LAN, Vlan ID  1., loopback not set

  Keepalive set (10 sec)

  Full-duplex, 100Mb/s, media type is RJ45

  output flow-control is XON, input flow-control is XON

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

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

  Last clearing of "show interface" counters 6w4d

  Input queue: 0/75/0/11667166 (size/max/drops/flushes); Total output drops:25467

  Queueing strategy: fifo

  Output queue: 0/40 (size/max)

  30 second input rate 3207000 bits/sec, 1372 packets/sec

  30 second output rate 6928000 bits/sec, 1777 packets/sec

     1438900212 packets input, 1979294624 bytes, 1 no buffer

     Received 132805 broadcasts, 0 runts, 0 giants, 1 throttles

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

     0 watchdog, 2124783 multicast, 0 pause input

     0 input packets with dribble condition detected

     213392395 packets output, 3395710852 bytes, 0 underruns

     0 output errors, 0 collisions, 0 interface resets

     132805 unknown protocol drops

     0 babbles, 0 late collision, 0 deferred

     0 lost carrier, 0 no carrier, 0 pause output

     0 output buffer failures, 0 output buffers swapped out

[Joseph W. Doherty]

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Posting

Understanding Flushes

The flushes counter in the show interface       atm command output increments as part of selective packet discard       (SPD), which implements a selective packet drop policy on the router's IP       process queue. Therefore, it applies to only process switched traffic.

The purpose of SPD is to ensure that important control packets, such as       routing updates and keepalives, are not dropped when the IP input queue is       full. When the size of the IP input queue is between the minimum and maximum       thresholds, normal IP packets are dropped based a certain drop probability.       These random drops are called SPD flushes.

Although the above is for an ATM interface, believe it applies to other interfaces too.

More information about SPD http://www.cisco.com/c/en/us/support/docs/routers/12000-series-routers/29920-spd.html, atlhough this is for 12k series, also believe it's similar on other devices that support SPD.