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What is the size of hardware queue on Ethernet interfaces?

Hi guys,

Does anyone know the size of hw queue on ethernet interfaces and how you can change it?

I have a 2811 router and I am trying to find out what is the size of its fastethernet hardware queue. I issued the command "sh controllers fastEthernet 0/0" and part of the response is :

Tx Rings

--------

Tx Ring 0                         Tx Ring 1

  - size        = 256              - size        = 0        

  - head        = 125              - head        = 0        

  - tail        = 125              - tail        = 0        

  - usedtxds    = 0                - usedtxds    = 0        

  - framecnt    = 0                - framecnt    = 0        

  - shadow      = 0x46EF4D80        - shadow      = 0x00000000

  - ring        = 0x0F1B63E0        - ring        = 0x00000000

  - ring_malloc = 0x3F1B63E0        - ring_malloc = 0x00000000

  Tx Ring 2                         Tx Ring 3

  - size        = 0                - size        = 0        

  - head        = 0                - head        = 0        

  - tail        = 0                - tail        = 0        

  - usedtxds    = 0                - usedtxds    = 0        

  - framecnt    = 0                - framecnt    = 0        

  - shadow      = 0x00000000        - shadow      = 0x00000000

  - ring        = 0x00000000        - ring        = 0x00000000

  - ring_malloc = 0x00000000        - ring_malloc = 0x00000000

  Tx Ring 4                         Tx Ring 5

  - size        = 0                - size        = 0        

  - head        = 0                - head        = 0        

  - tail        = 0                - tail        = 0        

  - usedtxds    = 0                - usedtxds    = 0        

  - framecnt    = 0                - framecnt    = 0        

  - shadow      = 0x00000000        - shadow      = 0x00000000

  - ring        = 0x00000000        - ring        = 0x00000000

  - ring_malloc = 0x00000000        - ring_malloc = 0x00000000

  Tx Ring 6                         Tx Ring 7

  - size        = 0                - size        = 0        

  - head        = 0                - head        = 0        

  - tail        = 0                - tail        = 0        

  - usedtxds    = 0                - usedtxds    = 0        

  - framecnt    = 0                - framecnt    = 0        

  - shadow      = 0x00000000        - shadow      = 0x00000000

  - ring        = 0x00000000        - ring        = 0x00000000

  - ring_malloc = 0x00000000        - ring_malloc = 0x00000000

As I can see fom this command the size of the hardware queue should be 256 packets (Am I right? Is this the right command to see?).

I have changed the queuing method on this fastethernet interface form the default, fifo, to wfq and also llq. When I reissued the command "sh controllers fastEthernet 0/0" nothing changed in the output. I tried also changing the depth of the hw queue manually by typing  "tx-queue-limit 20" and still nothing changed.

This is my conf on this interface:

interface FastEthernet0/0

bandwidth 512

ip address 10.1.120.110 255.255.255.0

tx-ring-limit 20

tx-queue-limit 20

duplex auto

speed auto

service-policy output Voce

end

Thanks for the help.

1 REPLY
Cisco Employee

Re: What is the size of hardware queue on Ethernet interfaces?

router has 2 type of Queues:

The Hardware Queue which is always FIFO, and the Software Queue determined by any Queuing Strategy to hold the packet.

Tx-ring limit defines the number of packet stored on the Hardward Queue before leaves a router.

see here for more info:

http://www.cisco.com/application/pdf/paws/6142/txringlimit_6142.pdf

You should not have to mess with this at all on an ethernet interface -

you should use the show policy-map xxx int x/y   command to view how the service policy is working.

Here is the QOS design guide for your reference:

http://www.cisco.com/en/US/docs/solutions/Enterprise/WAN_and_MAN/QoS_SRND/QoS-SRND-Book.html

Hope this helps,

Chester

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