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RE: Deferred packets on Full Duplex link [7:96300] posted 01/24/2005
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Here is what the sho int tells me:

FastEthernet0/1 is up, line protocol is up (connected)
  Hardware is Fast Ethernet, address is 000d.2989.7cc1 (bia 000d.2989.7cc1)
  MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full-duplex, 10Mb/s
  input flow-control is off, output flow-control is off
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:00:01, output 00:00:07, output hang never
  Last clearing of "show interface" counters 3d02h
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
  Queueing strategy: fifo
  Output queue :0/40 (size/max)
  5 minute input rate 0 bits/sec, 0 packets/sec
  5 minute ouxtput rate 0 bits/sec, 0 packets/sec
     1431307 packets input, 370478313 bytes, 0 no buffer
     Received 228785 broadcasts, 0 runts, 0 giants, 0 throttles
     2 input errors, 0 CRC, 2 frame, 0 overrun, 0 ignored
     0 watchdog, 160015 multicast, 0 pause input
     0 input packets with dribble condition detected
     2216156 packets output, 1401324783 bytes, 0 underruns
     0 output errors, 0 collisions, 0 interface resets
     0 babbles, 0 late collision, 75640 deferred
     0 lost carrier, 0 no carrier, 0 PAUSE output
     0 output buffer failures, 0 output buffers swapped out

Both pieces of equipment are Cisco, so wouldn't you figure that hard setting
both ports would be best? We've tried auto-negotiate in some other offices
like this, and they don't always auto-negotiate to the same duplex...which
obviously causes very serious performance problems. 

-----Original Message-----
From: Priscilla Oppenheimer [mailto:nobody@xxxxxxxxxxxxxx] 
Sent: Friday, January 21, 2005 12:12 PM
To: cisco@xxxxxxxxxxxxxx
Subject: RE: Deferred packets on Full Duplex link [7:96300]

Poulin, Darnell wrote:
> Hello all. We have a Catalyst 2950-24 (12.1(13)) that is
> showing an
> excessive number of deferred packets, causing packet loss on
> the network.
> The port that is showing the deferred packets is plugged into
> the Telco's
> WAN equipment (probably a Catalyst 2924), so we can't really
> check the other
> end. The deferred packets are happening at a rate of about
> 10000 an hour!
> There are no other errors showing up on the port (CRC, Frame,
> etc), and it
> is hard set to 10MB/Full Duplex.

Ought oh. Hard set. John Neiberger is going to whip you for that one! :-) 

The specs don't specify behavior when hard set and vendors do different
things. Unless you have to hard set it to make it work because of poor
implementations, you shouldn't do it. Use auto. See the archives for many
well-written explanations by John and others.

It appears that you are actually using half duplex. So when your interface
goes to send, it often hears that the other side is already sending, and has
to defer. On a busy half-duplex interface, where the other side sends a lot
of packets, defers are normal. They shouldn't occur on a full duplex link

What does show interface say? On some routers it will tell you what you're
really using rather than what you're configured to use.

Regardless, you should work with the telco and get both of the interfaces
set to auto negotiate. That usually works. It used to be avoided because it
often didn't work, but it is recommended these days by most people.


> Anybody know what else I should look for before calling the
> Telco to
> investigate?
> Thanks,
> Darnell.

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