Re: Total Output Drop on C2960G interface

+1 what Dale said;

When you have a 2960 or similar switch with small buffers and the inbound
rate > outbound rate because for example you have 4 interfaces receiving
data from hosts and a singular outbound interface, even if only for a very
short time (micro-burst) you will see output drops.

Potential solution: Increase outbound bandwidth capacity (Etherchannel etc)

On Mon, Oct 25, 2010 at 8:13 AM, Dale Shaw <dale.shaw_at_gmail.com> wrote:

> Hi,
>
> On Mon, Oct 25, 2010 at 6:52 AM, Abdul <rslab007_at_gmail.com> wrote:
> > Output que drops are a function of the recipient host (in your case, the
> firewall) unable to keep up with the data that is being sent by the switch.
> I am sure if you have the switchport enabled to send and receive Ethernet
> pause frames, you would see the a ton of input frames coming from the
> firewall.
> >
> > This problem isn't with your switch unable to keep up. It's with your
> firewall. Sure you could do things like policing your outbound traffic, but
> your probably better taking a more higher scope view as to what is the best
> QOS policies would be best suited and where (i.e where to mark your traffic)
> in your environment. Then executing your policies.
>
> I have to disagree. Output drops are caused when the switch runs out
> of buffers. 2960 is notoriously bad at coping with bursty traffic. I
> doubt it's got much at all to do with the firewall.
>
> Also, I recently read a post suggesting that enabling QoS on a 2960 is
> very likely to make it problem worse because it essentially causes the
> small amount of buffers to be carved up between 4 tx queues (I have no
> hands-on experience with c2960 so this is not authoritative).
>
> Cheers,
> Dale
>
>
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Received on Mon Oct 25 2010 - 09:23:25 ART