[c-nsp] lots of input errors & ignored

[Philippe Strauss]

Hello c-nsp,

I have a c7401 running c7400-is-mz.124-13b.bin with "no ip pxf" acting
as an ADSL LNS showing high rate on one of it's interface of "input errors"
and "ignored". It comes in burst, not incrementing during one minute or so,
then during ~10 seconds, it increase of 20 to 1000 packets!
overall, it's near 1% input packet dropped.
Usually (as the doco says at least) it's related to buffers, but I can't
see the "show buffers" output increamenting ("misses" values) for any sized
buffers, nor in the Fa1/0 private particle buffers.
sh controller fa1/0 gives the exact same number as "ignored" under "RX No Buff".there's a rate limit to 10Mbps in/out on this interface, but
"show int fa1/0 rate" gives very different numbers.

rt-cc-lns1#sh int fa1/0
FastEthernet1/0 is up, line protocol is up
  Hardware is i82543 (Livengood), address is 000b.fcc4.d81c (bia 000b.fcc4.d81c)
  Description: ADSL Home
  Internet address is 195.70.20.18/30
  MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
     reliability 255/255, txload 4/255, rxload 21/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full-duplex, 100Mb/s, 100BaseTX/FX
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:00:06, output 00:00:00, output hang never
  Last clearing of "show interface" counters 01:08:11
  Input queue: 0/75/34/0 (size/max/drops/flushes); Total output drops: 0
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 8294000 bits/sec, 1052 packets/sec
  5 minute output rate 1856000 bits/sec, 769 packets/sec
     3965119 packets input, 3548670736 bytes
     Received 0 broadcasts, 0 runts, 0 giants, 12 throttles
     27965 input errors, 0 CRC, 0 frame, 0 overrun, 27965 ignored <--- !!!!!!!
     0 watchdog
     0 input packets with dribble condition detected
     2751492 packets output, 909061474 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

regards.

-- 
Philippe Strauss
av. de Beaulieu 25
1004 Lausanne
http://philou.ch