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.
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