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New Member

Reg Output drops on Gig interface

Dear All,

I have core 6509 switch in our data center connecting to 7206 router with gig interface both the sides. I am observing output drops occuring on switch end and the drops are not occuring continuesly, its happening intermetently.

Both the sides are full duplex and speed 100 is configured and at the same time router end interface was not dropping packets.

-----------------------

GigabitEthernet7/36 is up, line protocol is up (connected)

Hardware is C6k 1000Mb 802.3, address is 0015.fa02.268f (bia 0015.fa02.268f)

Description: ***************

MTU 1500 bytes, BW 100000 Kbit, DLY 10 usec,

reliability 255/255, txload 53/255, rxload 22/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Full-duplex, 100Mb/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 00:00:57, output hang never

Last clearing of "show interface" counters 00:00:06

Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 693

Queueing strategy: fifo

Output queue: 0/40 (size/max)

5 minute input rate 8883000 bits/sec, 5492 packets/sec

5 minute output rate 20941000 bits/sec, 5471 packets/sec

25985 packets input, 5001283 bytes, 0 no buffer

Received 4 broadcasts (4 multicasts)

0 runts, 0 giants, 0 throttles

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

0 watchdog, 0 multicast, 0 pause input

0 input packets with dribble condition detected

24942 packets output, 10994588 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 PAUSE output

0 output buffer failures, 0 output buffers swapped out

--------------------

#sh int g7/36 | inc flush

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

#sh int g7/36 | inc flush

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

#sh int g7/36 | inc flush

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

#sh int g7/36 | inc flush

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

#sh int g7/36 | inc flush

Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 188

#sh int g7/36 | inc flush

Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 188

#sh int g7/36 | inc flush

Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 1362

-----------------

Above are the logs caputred during packet drops. Kindly advise what are the possibilites for dropping packets.

Regards,

Gopal

11 REPLIES

Re: Reg Output drops on Gig interface

Typically output drops occurs when line is congested. it does not seem to be the case here.

your load is 20% and running full duplex.

1-what is the load on adjacent interface ?

2-turn off ur flow control. "(config-if)#flowcontrol send off

"

http://www.cisco.com/en/US/products/hw/routers/ps133/products_tech_note09186a0080094791.shtml#drops

HTH

Sam

Hall of Fame Super Silver

Re: Reg Output drops on Gig interface

Hello,

I see that output flow-control is on, so I wonder if it could be the c7206 sending IEEE pause frame to cause the small output drops you see.

Otherwise, you have to look at what type of linecard you have: you could experience performance troubles on older 48GE linecards where groups of n ports share the same cpu/resources and connection to the backplane is only 8Gbps.

there has been another thread about this.

hope to help

Giuseppe

New Member

Re: Reg Output drops on Gig interface

Dear Giuseppe,

How do i check which line card is being used.

Regards

Gopal

Re: Reg Output drops on Gig interface

Cat6k#show module

Please rate helpful posts.

Best Regards,

Mounir Mohamed

Re: Reg Output drops on Gig interface

Hi,

Total output drops counter increased because the output queue is full, a common cause of this might be traffic from a high bandwidth link being switched to a lower bandwidth link or traffic from multiple inbound links being switched to a single outbound link

For example if there is a group of FE 100 interfaces connected to Data Center Servers trying to send traffic behind your router (7206) the output queue may get full which is cause the output drops counter to be increased

So start monitoring input traffic from your router or even the output traffic pattern on the Catalyst interface (G7/36) so it's bandwidth problem you have to change the port speed from BOTH sides to be 1000 instead of 100

Note that the interface output queue doesn't change if the speed increased, but the switch will be able to switch frames fastly with line rate 1000 instead of 100

Also in your case flow-control might be the cause of the problem.

The below URL for Troubleshooting Switch Port and Interface Problems:

http://www.cisco.com/en/US/products/hw/switches/ps700/products_tech_note09186a008015bfd6.shtml#giga

Best Regards,

Mounir Mohamed

New Member

Re: Reg Output drops on Gig interface

Hi,

CEF720 48 port 10/100/1000mb Ethernet - is the module being used in our switch.

Regards

Gopal

Re: Reg Output drops on Gig interface

Gopal

The problem is very likely flow control, are u able to disable it and test ?

Sam

New Member

Re: Reg Output drops on Gig interface

Hi Sam,

Could you provide me some links to get more clarity why flow control is causing this issue. Using that only i can change the config on the core boxes.

Regards,

Gopal

Re: Reg Output drops on Gig interface

Hi Gopal

Pay special attention to the fact that if u need predictable results u need to follow guidelines below.

How is other end configured, flow control receive off?

Flow control can be useful, but from my own experience I have learn to remove it. I am using WS-X6724-SFP on 7600 chassis.

HTH

Sam

http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2ZY/command/reference/I1.html#wp1084927

To obtain predictable results, follow these guidelines:

•Use send on only when remote ports are set to receive on or receive desired.

•Use send off only when remote ports are set to receive off or receive desired.

•Use receive on only when remote ports are set to send on or send desired.

•Use send off only when remote ports are set to receive off or receive desired.

New Member

Re: Reg Output drops on Gig interface

Hi Sam,

Router end gig port is configured for flow control ON.

----------------------------

GigabitEthernet0/0 is up, line protocol is up

Hardware is BCM1125 Internal MAC, address is 0016.9de5.4810 (bia 0016.9de5.4810)

Internet address is 10.223.252.129/29

MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,

reliability 255/255, txload 6/255, rxload 10/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Full-duplex, 100Mb/s, media type is RJ45

output flow-control is XON, input flow-control is XON

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

Last input 00:00:02, output 00:00:00, output hang never

Last clearing of "show interface" counters 31w3d

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

Queueing strategy: fifo

Output queue: 0/40 (size/max)

30 second input rate 4187000 bits/sec, 1483 packets/sec

30 second output rate 2641000 bits/sec, 1415 packets/sec

Silver

Re: Reg Output drops on Gig interface

What is the type of linecard that is reporting the output drops? Send a show mod from the switch.

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