[cisco-bba] Can you run PQ/CBWFQ on 3640 Ethernet IF?

Dennis Peng dpeng at cisco.com
Wed Jul 23 10:10:33 EDT 2003

Queuing will only have a noticeable effect if packets build up in the
queue. Without a sizeable queue to actively manage, any sort of fancy
queueing is equivalent to FIFO. Usually packets will only build up if
packets are being routed to an outbound interface at a sustained rate
greater than the interface can transmit at. This usually occurs for
low-speed links like serial interfaces and not so much for LAN
interfaces like ethernet. Not to say you couldn't overload a ethernet
interface, just that it is less common. You can look at the output
queue in "show interface". If the output queue is usually 0/40, then
you aren't building up packets in the queue and any type of queueing
will have essentially no effect.


Paul Plantinga [p.plantinga at ee.wits.ac.za] wrote:
> Hello,
> I'm fairly new to this but am running IOS 12.1(5)T on a cisco3640 and am trying to implement some/any priority queueing of my voice on a 10Mg Ethernet IF. It seems that you can configure anything.. but that doesn't mean it will run, so from the release notes it appears I cannot do CBWFQ or PQ on this interface, however the Cisco feature navigator says I can. I tried to test them both and it seems that they are matching correctly and being queued correctly but changing the voice class queue limit seems to have no effect on the delay of my udp packets (i.e. they are being queued behind the tcp no matter?). So are the config commands being ignored? (but my packet losses indicate some effect in changing queue limit).
> Ultimately, what form of PQ can I run for voice in my setup?
> Regards
> Paul

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