[c-nsp] issues with 6500 platform

[Pete Lumbis]

I would suggest starting with captures on both sides of the 6k to see
what is happening at the TCP layer (out of order packets, dropped
packets). From there I'd look at features enabled on the interface to
see what might be messing with things (e.g., QoS, tcp adjust-mss, ect)
and try to narrow down the culprit from there.

On Tue, Feb 8, 2011 at 1:05 AM, Jason Cardenas
<jason.cardenas79 at gmail.com> wrote:
> Good day, Cisco-NSP!
>
> We've ran into an odd issue with Cisco 6504 with SUP720-3BXL running
> 122-33.SXH.
>
> A system (or systems) with multiple IP addresses, same MAC or different MACs
> for all IP addresses getting unusually slow download speeds and it seems to
> be src-ip related.
>
> #1 IP: xx.xx.xx.31 ; wget from a remote host grabs a file @ 8-10M/s speed
> (optimal speed, let's pretend)
> #2 IP: xx.xx.xx.32 ; @ 300K/s identical file - [FreeBSD ISO (432M)]
> #3 IP: xx.xx.xx.33 ; @ 800K/s identical file, etc
>
> We isolated this to a specific device, our core Cisco 6504. Forcing outgoing
> traffic to go via alternative transit providers did not change overall
> picture. Upstreams are not saturated in any way. Transfer rates stay at the
> same levels for the above IP addresses. It looks like that across our entire
> network. Pretty random stuff. Changing OS on the server - no change.
> Changing MACs - no change either.
>
> We also tried to wget from different locations as well, in terms of the
> speed everything stays the same across all of the above IP addresses. We're
> positive that this is related to src-ip.
>
> Yet, what's weird is that within our internal network download speeds
> 80-90M/s+ are easily achieved from same IPs that are 'slow' from the
> outside!
>
> Could it be QoS-related, ISO bug? What else could it be?
>
> Please, let me know what other information may be required to solve this
> mystery. Thanks!
>
> Jason
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