[c-nsp] EtherChannel on WS-X6148-GE-TX

[Matt Buford]

> It's been documented numerous times that WS-X6148-GE-TX can't push more 
> than
> 1 Gbps on a given EtherChannel. Is this a per-card limitation? E.g. would 
> it
> be possible to push more than 1 Gbps if the EtherChannel member ports were
> on different blades? I'm using a 6509 with Sup1a/MSFC running 12.1E.

Short answer:

If any port within an etherchannel lies within a WS-6148-GE-TX card, that 
etherchannel now has a 1gig limit.  In fact, it is likely less than 1gig. 
These cards are already heavily oversubscribed.

First, understand that there is a 1gig ASIC for every group of 8 ports on 
the card.

Second, understand that when you enable Etherchannel, all packets for the 
entire bundle are flooded to all member ASICs.  It is then up to the ASIC to 
filter out and pass on only the packets that are for that specific port.

Combine those two concepts and you can see the limitation.  On top of that, 
if the other 7 ports in the same ASIC are busy too you can easily end up 
with a limitation well below 1gig.

Long answer:

http://www.cisco.com/warp/public/473/4.html#cat6k

scroll down to the "Restrictions" part of this section.