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Pause Outputs on Interfaces

I have on some interfaces on my Cisco 6506 (Version 12.2(18)SXF)pause outputs.

Does somebody has an idea how to fix this?

My Interfaceconfig is

interface GigabitEthernet3/41


switchport trunk allowed vlan 2-12,30

switchport mode trunk

no ip address

speed 1000

duplex full


and show interface is

GigabitEthernet3/41 is up, line protocol is up (connected)

Hardware is C6k 1000Mb 802.3, address is 0014.a9df.0c38 (bia 0014.a9df.0c38)

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

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

Clock mode is auto

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

Last input never, output 00:00:23, output hang never

Last clearing of "show interface" counters 1w1d

Input queue: 0/2000/0/0 (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 output rate 11000 bits/sec, 17 packets/sec

18042194 packets input, 22793525691 bytes, 0 no buffer

Received 8213 broadcasts (5 multicasts)

0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 7 frame, 0 overrun, 0 ignored

0 watchdog, 0 multicast, 0 pause input

0 input packets with dribble condition detected

19288722 packets output, 6685319847 bytes, 0 underruns

0 output errors, 0 collisions, 0 interface resets

0 babbles, 0 late collision, 0 deferred

0 lost carrier, 0 no carrier, 43240 PAUSE output

0 output buffer failures, 0 output buffers swapped out


Re: Pause Outputs on Interfaces

Hi there,

AFAIK the pause output counter refers to the number of PAUSE frames recieved by a port.

That being the case, I found this explanation for the counter that you describe

The number of PAUSE frames recieved by this port. The PAUSE frame must have a valid MAC Control Frame EtherType field (88-08h), have a destination MAC address of either the MAC Control frame reseved multicast address (01:80:C2:00:00:01), be a minimum of 64 bytes long (excluding preamble but including Frame Check Sequence), and have a valid CRC. Although an 802.3 compliant MAC is only permitted to transmit PAUSE frames when in full duplex mode with flow control enabled and with the transfer of PAUSE frames determined by the result of autonegotiation, an 802.3 MAC receiver is required to count all received PAUSE frames, regardless of its half/full-duplex status.

An indication that a MAC is in half-duplex mode with this counter incrementing indicates a non-compliant transmitting device on the network.

Since your duplex is full I dont know what to make of it now though :S Maybe these were frames that were transmitted by the other end while attempting an auto negotiation?


Please rate posts that help




Re: Pause Outputs on Interfaces


I see that you output flowcontrol is enabled. Your TCP application that reside on that port is sending pause frames, you can try to disable the flowcontrol feature or locate the application/host that generates the pause frames.

flowcontrol send

Enables transmission of outgoing pause frames. The following options can be configured with this command:

* desired - Allows, but does not require, outgoing pause frames to leave the interface.

* off - Disables transmission of outgoing pause frames.

* on - Enables transmission of outgoing pause frames



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Re: Pause Outputs on Interfaces

This is appearently caused by the flow control that is active on the switch: input flow-control is off, output flow-control is on

Please check the following for more details: