[c-nsp] fabric switching enable

[Richard A Steenbergen]

On Tue, Jun 17, 2008 at 12:35:41PM -0700, Pham, Loc wrote:
>    How can I identify whether our module is switched on mix mode and how
> to change it ? any gotcha ?

It won't change out of bus mode until you have more than one fabric 
enabled card. After all, what is the point of using the fabric if you have 
no one else to talk to over it. If you really want to fiddle with this, 
for some reason I can't imagine, look at:

router(config)#fabric switching-mode allow truncated ?
  threshold  Number of SFM-capable modules for truncated switching mode. Switch
             applies the threshold only when the mode is disallowed. Switch
             ignores the threshold when the truncated mode is allowed

The default is 2. The reason that you might want to set this higher than 2 
is that turning on truncated mode switching without actually switching 
packets over the fabric (i.e. you're sending all the packets to bus-only 
cards) actually increases bus utilization. In bus mode you just write the 
entire data packet onto the bus, in truncated mode you switch the data 
packet AND have to put the first 64 bytes of the packet onto the bus to do 
the routing lookup on a PFC.

On Tue, Jun 17, 2008 at 11:27:23PM +0200, Peter Rathlev wrote:
> Changing switching mode power cycles the modules by the way. I guess
> that's a gotcha. :-)

I'm pretty sure thats not true. You may be thinking of PFC/DFC modes, 
where inserting a "lower" capability card (3a or 3b into a 3bxl system, 
etc) brings down the entire switch to the lowest common card, and requires 
a reboot of the entire system to bring it back (after removing the 
offending card of course). This doesn't happen to the switching mode at 
all.

-- 
Richard A Steenbergen <ras at e-gerbil.net>       http://www.e-gerbil.net/ras
GPG Key ID: 0xF8B12CBC (7535 7F59 8204 ED1F CC1C 53AF 4C41 5ECA F8B1 2CBC)