[c-nsp] Cisco 650x sup2 / sup32 configuration - what makes sense?

Seth Mattinen sethm at rollernet.us
Thu Dec 8 12:29:36 EST 2011

On 12/8/11 7:58 AM, Jon Lewis wrote:
> On Thu, 8 Dec 2011, Gert Doering wrote:
>> The best choice?  Don't use 6148-GE-TX modules.  They are fundamentally
>> broken (8 ports share one ASIC with a single-GE uplink, one port that's
>> "full" will block out the other 7 ports, ...).  It's even worse if
>> you use them for 100M links, because a saturated 100M link will eat
>> all the buffers from the other 7 ports on the same ASIC, causing RTT
>> jumps on these other ports.
> Just to clarify, as I understand it, this (shared buffers) is an issue
> with the 6148-GE-TX, but not with the 6148A-GE-TX, which according to
> cisco documentation has much larger buffers and they're per port, not
> shared by the ports in each 8 port group.  The 6148A-GE-TX is still 8:1
> oversubscribed, so it's a poor choice if you have a need for lots of
> 1000baseT ports handling much traffic, but at least it has nice per-port
> buffers.  I suspect if most of the ports are used as 100baseT, and you
> have the occasional 1000baseT port that might carry just a little more
> than 100mbit/s, it should do fine.

And the 6148A supports jumbo frames, if that matters. But yeah, it has
2.6MB per port buffers instead of 1MB shared across 8 ports.


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