High Output drops on Catalyst 4507

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May 24th, 2007
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Hello, I have a catalyst 4507 with a WS-X4418-GB blade. The ports on the blade are trunks connected to 3560 edge switches. whenever the ports begin to transmit more than 10Mbps, I will see total output drops in the order of 1M to 3M per day. The first two ports on this blade do not experience drops, but the rest of the ports do. Why am i seeing such large output drops on low utilized Gig ports?

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bjornarsb Thu, 05/24/2007 - 11:17
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Have you enabeled layer 2 flow control ?

Try disable it and see how it goes.



bssmith10 Thu, 05/24/2007 - 11:58
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is layer 2 flow control enabled by default? I have never specifically configured it.

scottmac Thu, 05/24/2007 - 15:51
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Check your cabling (specifically, the jumpers) between the switches. A split pair on pins 3&6 will cause this kind of behaviour and is very common in handmade cables (or "bad" cables - kinked, twisted, severe bends, stretched, crushed, etc).

The issue is too much crosstalk on the cable (10Meg is half duplex ... crosstalk doesn't interfere because only one side is talking at a time).

Good Luck


bssmith10 Thu, 05/24/2007 - 16:56
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Unfortunately these are fiber connections. Actually I beleive that I am running into oversubscription on the ports. In my original question I stated the type of blade and noted that only ports 1&2 are the only ones not dropping packets. That is because these two ports each have 1Gbps of bandwidth whereas the other ports share 1Gbps in groups of four.

bjornarsb Thu, 05/24/2007 - 23:36
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post a show interface, and we will see if its enabeled :)

bssmith10 Fri, 05/25/2007 - 05:50
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GigabitEthernet3/6 is up, line protocol is up (connected)

Hardware is Gigabit Ethernet Port, address is 0014.1cf1.dfd5 (bia 0014.1cf1.dfd5)

Description: CONNECTION TO floor17switch2

MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Full-duplex, 1000Mb/s, link type is auto, media type is 1000BaseSX

input flow-control is off, output flow-control is off

ARP type: ARPA, ARP Timeout 04:00:00

Last input 00:00:01, output never, output hang never

Last clearing of "show interface" counters 2d20h

Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 19355213

Queueing strategy: fifo

Output queue: 0/40 (size/max)

5 minute input rate 173000 bits/sec, 93 packets/sec

5 minute output rate 209000 bits/sec, 113 packets/sec

16469604 packets input, 3816069975 bytes, 0 no buffer

Received 437375 broadcasts (409350 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

77597273 packets output, 90385565725 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


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