Options for Queueing Strategies for 3750 Switch

Unanswered Question
Apr 22nd, 2009

Does the 3750 FastEthernet ports provide any other queueing option than FIFO?

I have this problem too.
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Edison Ortiz Wed, 04/22/2009 - 12:58

3750 supports fair-queuing and random-detect as well.

Rack1SW1#sh run int f0/1

Building configuration...

Current configuration : 72 bytes


interface FastEthernet0/1

switchport access vlan 14



Rack1SW1#sh int f0/1 | i Queueing

Queueing strategy: weighted fair


Rack1SW1#sh int f0/1 | i Queueing

Queueing strategy: random early detection(RED)

For more information, refer to the documentation:





pmoscatelli Wed, 04/22/2009 - 13:24

Thanks much Edison.

Here's my problem. My 3750 does not have these queueing commands available for my FastEthernet ports.

Here's what I have

cisco WS-C3750-48TS (PowerPC405)

(C3750-IPSERVICESK9-M), Version 12.2(50)SE

Edison Ortiz Wed, 04/22/2009 - 13:30

That's odd. My output above was taken from a 3560 running 12.2(25)SEE - sorry I don't have a 3750 switch at the moment but both should share the same set of commands.

Do you have the port configured in layer2 mode (switchport) or layer3 mode (no switchport)?



pmoscatelli Wed, 04/22/2009 - 13:40

Layer-2 with Q-Trunking

interface FastEthernet1/0/1


switchport trunk encapsulation dot1q

switchport mode trunk

bandwidth 45000

load-interval 30

speed 100

duplex full

srr-queue bandwidth limit 10

spanning-tree portfast

Edison Ortiz Thu, 04/23/2009 - 07:50


After further research, the commands I demonstrated on my original post are/were available in some version of IOS in the Catalyst switches but they aren't supported on that type of hardware.

The available queueing strategies are described in the link I provided, which are: WTD and SRR.

I see you are using SRR for bandwidth limiting and you can also use SRR for sharing and shaping of queues.

Please take a moment and read the link I provided on the 2 queuing options available. The 3750 has limited options in term of QoS as its marketed as a desktop switching solution, not a distribution|core switching solution.

You may also benefit from reading the QoS SRND:





Joseph W. Doherty Wed, 04/22/2009 - 16:00

"Does the 3750 FastEthernet ports provide any other queueing option than FIFO?"

Yes and no. The 3750 provides 4 output FIFO queues per interface with weighted tail drop. The reference Edison provided explains further (although you should use the manuals for your release [which he didn't know at the time he provided it]).


Regarding Edison noting FQ support in his release but not found in yours, the configuration guide, for his version, notes in Appendix C, page C-5, it's an unsupported interface command, see http://www.cisco.com/en/US/docs/switches/lan/catalyst3560/software/release/12.2_25_see/configuration/guide/3560SCG.pdf

pmoscatelli Thu, 04/23/2009 - 07:20

Okay. So I downloaded the configuration guide, but I'm not really following you. Sorry.

I've read lots of manuals and couldn't find anything about queuing other than what I see defined on the interface by default (FIFO). Can someone show me on a 3750 running this release?


pmoscatelli Mon, 04/27/2009 - 05:16

Sorry about the delayed response. Here's a "show interface" output. Queueing Strategy is FIFO.


MRHONGCG01RGW01#show int fa1/0/1

FastEthernet1/0/1 is up, line protocol is up (connected)

Hardware is Fast Ethernet, address is 000f.34f0.1b03 (bia 000f.34f0.1b03)


MTU 1500 bytes, BW 45000 Kbit, DLY 100 usec,

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

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Full-duplex, 100Mb/s, media type is 10/100BaseTX

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

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

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

Last clearing of "show interface" counters 4d16h

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

Queueing strategy: fifo

Output queue: 0/0 (size/max)

30 second input rate 6000 bits/sec, 8 packets/sec

30 second output rate 3000 bits/sec, 4 packets/sec

3366507 packets input, 595882008 bytes, 0 no buffer

Received 2440100 broadcasts (2440060 multicasts)

0 runts, 0 giants, 0 throttles

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

0 watchdog, 2440060 multicast, 0 pause input

0 input packets with dribble condition detected

1822391 packets output, 480478260 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


Joseph W. Doherty Mon, 04/27/2009 - 06:47

I suspect an "regular" show interface may not accurately depict output queuing on a 3750. You can also see in your stats "Output queue: 0/0 (size/max", and I doubt the maximum queue size is zero.

pmoscatelli Tue, 04/28/2009 - 13:13

Okay. I appreciate your suppport.

So, where are we at. Not sure if we've answered the question on queueing strategy?

Joseph W. Doherty Tue, 04/28/2009 - 13:34

The 3750 supports 4 FIFO queues per interface. There are options on how each is dequeued relative to others, how buffers space is allocated, and various tail drops limits. The QoS chapter in the configuration guide explains these feature. If you have not read it, suggest you do. If you still have questions, post again.


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