From: Peasah, Richard Kwame (rpeasah@ku.edu)
Date: Sun Sep 26 2004 - 19:55:17 GMT-3
Folks,
Can I borrow your brains for a few minutes? My internet router, a Cisco
7304, is dropping packets from the input queue and I'm having a tough
time figuring out the cause. Over the past 2 weeks there've been
instances where all of a sudden it will drop all packets for minutes and
then resume forwarding. It's been hard nailing down the exact time this
behavior occurs. By the time I'm alerted by the help desk, the incident
is over and the router is back forwarding packets. However, I'm seeing
lots of flushing going on with respect to the input queue for the
interface connecting to our ISP. See three instance of "show int"
output below:
Last clearing of "show interface" counters 03:01:42
Input queue: 0/75/216/4427 (size/max/drops/flushes); Total output drops:
2901
Last clearing of "show interface" counters 03:51:56
Input queue: 1/75/238/6161 (size/max/drops/flushes); Total output drops:
3280
Last clearing of "show interface" counters 05:05:08
Input queue: 1/75/269/8047 (size/max/drops/flushes); Total output drops:
4443
Since I don't have a baseline to compare with I really can't tell
whether this is normal (the flushes and the drops) but it sure doesn't
look normal to me. Anyone with experience with this stuff please shed
some light on this, please. I've both cef and fast switching configured
and I'm not seeing any cache misses so far. At this point, one thing
jumping at me is the "bad hop count" in the "sh ip traffic" output. This
counter keeps incrementing as can be see below:
08:00 7242548
10:00 7267491
12:00 7314403
15:00 7387856
16:00 7402531
17:00 7419743
I've been scouring CCO for some pointers without success. Some technotes
suggest I turn on "debug ip error" but I'm really reluctant (actually
scared) to do that for fear of taking the whole damn thing down. This is
our only internet node so until I get a nod for them "Big Kahunas" I
ain't doing no debugging. Any ideas? And oh, I've been checking my
buffers and so far no misses there.
Richard Peasah, Ph.D., CCIE 13662
Networking & Telecommunications Services
University of Kansas
rpeasah@ku.edu
(785) 864-9354
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