[c-nsp] Nexus 5k dual sup design

[JP Velders]

> Date: Thu, 23 May 2013 08:44:36 -0700
> From: manderson <chiefwfb at gmail.com>
> Subject: [c-nsp] Nexus 5k dual sup design

> Hello, we currently use a single sup design in one of our DC's and we're
> playing w/a dual sup design for single homed servers in our other DC.
>  Cisco A/S, our SE, and myself are not particularly fond of the dual sup
> design.  However, the lead engineer appears to be set on going this route.

> Other than having two different architectures at two different DC's, and
> designing a network to support single homed servers, I'm looking for
> additional pros/cons as points of discussion.

Dual-homing FEX'es allows for lower impact on upgrades (and has been a 
saver before, given that weird stuff happens on NXOS).

However, a dual-homed FEX does _not_ allow for LAGs downstream (to 
dual home a server in active/active mode), at least on the 1st gen 
FEXes we have, and that stupidity (together with all the STP 
limitations) has steered me away from N2/5K for real datacenters.

Do make sure to look at any vPC setup with an almost pessimistic view 
to work out all the failure scenarios and design accordingly.

Also remember that in a dual-homed FEX setup you need to duplicate 
everything on both N5K's, and inconsistencies can be impacting.

Kind regards,
JP Velders