[nsp] Cisco 3524 ignored packets

[Simon Lockhart]

I'm in the middle of trying to diagnose a strange packet loss problem on one of
our LANs. The nearest I can get to isolating the problem is that when I get a
bad burst of packet loss, the ignored count on one of the switches in the path
goes up significantly.

FastEthernet0/5 is up, line protocol is up 
  Hardware is Fast Ethernet, address is 0030.946d.7705 (bia 0030.946d.7705)
  MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec, 
     reliability 255/255, txload 20/255, rxload 21/255
  Encapsulation ARPA, loopback not set
  Keepalive not set
  Auto-duplex (Full), Auto Speed (100), 100BaseTX/FX
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:00:07, output 00:00:01, output hang never
  Last clearing of "show interface" counters 00:36:47
  Queueing strategy: fifo
  Output queue 0/40, 0 drops; input queue 0/75, 0 drops
  5 minute input rate 8432000 bits/sec, 2154 packets/sec
  5 minute output rate 8097000 bits/sec, 2041 packets/sec
     4833762 packets input, 2403042086 bytes
     Received 2344769 broadcasts, 0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 10919 ignored
     0 watchdog, 2344712 multicast
     0 input packets with dribble condition detected
     4667093 packets output, 2461139718 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

Is this likely to be caused by the amount of multicast traffic? Is it exhausting all the
buffers? Working from the packet counts, it's less than 5Mbps of Multicast - surely
the 3524 should be able to cope with this?

Any ideas?

Simon
-- 
Simon Lockhart     |   Tel: +44 (0)1628 407720 (x(01)37720) | Si fractum 
Technology Manager |   Fax: +44 (0)1628 407701 (x(01)37701) | non sit, noli 
BBC Internet Ops   | Email: Simon.Lockhart at bbc.co.uk        | id reficere
BBC Technology, Maiden House, Vanwall Road, Maidenhead. SL6 4UB. UK