Total output drops increase!

ifabrizio · ‎05-03-2016

Dear All,

I have a Cisco 4500 Version 03.03.01.XO like this:

Power consumed by backplane : 40 Watts

Mod Ports Card Type                              Model              Serial No.
---+-----+--------------------------------------+------------------+-----------
1    48 10/100/1000BaseT Premium POE E Series WS-X4748-RJ45V+E
2    48 10/100/1000BaseT Premium POE E Series WS-X4748-RJ45V+E
3    48 10/100/1000BaseT EEE (RJ45)            WS-X4748-RJ45-E
4    48 10/100/1000BaseT EEE (RJ45)            WS-X4748-RJ45-E
5     8 Sup 8-E 10GE (SFP+), 1000BaseX (SFP)   WS-X45-SUP8-E
6     8 Sup 8-E 10GE (SFP+), 1000BaseX (SFP)   WS-X45-SUP8-E
7    48 10/100/1000BaseT EEE (RJ45)            WS-X4748-RJ45-E
8    48 10/100/1000BaseT EEE (RJ45)            WS-X4748-RJ45-E

M MAC addresses                    Hw Fw           Sw               Status
--+--------------------------------+---+------------+----------------+---------
1 d072.dcfa.96d0 to d072.dcfa.96ff 1.5                               Ok
2 d072.dcfa.9820 to d072.dcfa.984f 1.5                               Ok
3 7426.ac4e.a984 to 7426.ac4e.a9b3 1.2                               Ok
4 7426.ac4e.9ba4 to 7426.ac4e.9bd3 1.2                               Ok
5 b838.61fd.d840 to b838.61fd.d847 1.1 15.1(1r)SG1 03.03.01.XO      Ok
6 b838.61fd.d848 to b838.61fd.d84f 1.1 15.1(1r)SG1 03.03.01.XO      Ok
7 7426.ac4e.b7f4 to 7426.ac4e.b823 1.2                               Ok
8 7426.ac4e.92a4 to 7426.ac4e.92d3 1.2                               Ok

Mod Redundancy role     Operating mode      Redundancy status
----+-------------------+-------------------+----------------------------------
5   Active Supervisor   SSO                 Active
6   Standby Supervisor SSO                 Standby hot

I have a problem on some Gigabit ports, the Total output drops increase:

GigabitEthernet8/15 is up, line protocol is up (connected)
Hardware is Gigabit Ethernet Port, address is 7426.ac4e.92b2 (bia 7426.ac4e.92b2)
Description: DIREZIONE1
MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100 usec,
     reliability 255/255, txload 2/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 100Mb/s, link type is auto, media type is 10/100/1000-TX
input flow-control is on, output flow-control is on
Auto-MDIX on (operational: on)
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:14, output never, output hang never
Last clearing of "show interface" counters never
Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 25073794
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 835000 bits/sec, 310 packets/sec
     68938373 packets input, 5973744151 bytes, 0 no buffer
     Received 59423 broadcasts (59050 multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 input packets with dribble condition detected
     986562089 packets output, 220966643648 bytes, 0 underruns
     0 output errors, 0 collisions, 3 interface resets
     0 unknown protocol drops
     0 babbles, 0 late collision, 0 deferred
     0 lost carrier, 0 no carrier
     0 output buffer failures, 0 output buffers swapped out

Follow the port config:

interface GigabitEthernet8/15
switchport mode access
spanning-tree portfast
spanning-tree guard root

Could you help me to understand why?

Bye,

Igor.

Joseph W. Doherty · ‎05-03-2016

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The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

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In no event shall Author be liable for any damages wha2tsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

The usual cause is data arrives faster than the port can transmit it.

ifabrizio · ‎05-08-2016

Hi Joseph and All,

I finally I have found why Total output drops, increase the problem is not a performance problem, indeed the interface buffer is empty.

But it is caused by cable Category that it is the "5" (not 5E).

Using a cable category 6A it all OK.

Best regards,

Igor.

Joseph W. Doherty · ‎05-09-2016

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages wha2tsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

Well that's a surprise. I wouldn't expect the cable to cause egress drops, unless the volume of traffic was much higher, due to L3 traffic being retransmitted, due to receiver loss due to frame corruption.

ifabrizio · ‎05-18-2016

Hi Joseph,

The problem is caused by Cable Category 5 with 1000Base-Tx Cards.

This cards do not works correctly with category 5. But only with category 6 see the link below:

http://web.archive.org/web/20110927060633/http://www.tiaonline.org/news_events/press_room/press_releases/legacy.cfm?parelease=01-87